:root {
      color-scheme: light;
      --bg: #f6f7f9;
      --surface: #ffffff;
      --surface-2: #f0f2f5;
      --surface-3: #e7eaf0;
      --text: #16181d;
      --muted: #667085;
      --subtle: #8792a2;
      --line: #d8dde6;
      --accent: #1967d2;
      --accent-2: #0f766e;
      --danger: #c24133;
      --warning: #b45309;
      --warning-slash: #e65100;
      --shadow: 0 16px 42px rgba(16, 24, 40, 0.12);
      --radius: 8px;
      --ui-font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
      --chart-font: "SFMono-Regular", ui-monospace, Menlo, Consolas, "Liberation Mono", monospace;
      --app-font-size: 15px;
      --editor-font: 15px;
      --preview-font: 14px;
      --presentation-font: 42px;
      --editor-line: 1.6;
      --panel-pad: 16px;
      --tap-size: 40px;
    }

    html[data-theme="dark"] {
      color-scheme: dark;
      --bg: #0f1115;
      --surface: #17191f;
      --surface-2: #21252d;
      --surface-3: #2d333f;
      --text: #e2e8f0;
      --muted: #94a3b8;
      --subtle: #64748b;
      --line: #333b4d;
      --accent: #60a5fa;
      --accent-2: #2dd4bf;
      --danger: #f87171;
      --warning: #fbbf24;
      --warning-slash: #f59e0b;
      --shadow: 0 20px 60px rgba(0, 0, 0, 0.45);
    }

    html[data-accent="teal"] {
      --accent: #0f766e;
      --accent-2: #2563eb;
    }

    html[data-accent="rose"] {
      --accent: #c02660;
      --accent-2: #7c3aed;
    }

    html[data-accent="amber"] {
      --accent: #b45309;
      --accent-2: #15803d;
    }

    html[data-accent="violet"] {
      --accent: #6d28d9;
      --accent-2: #0891b2;
    }

    html[data-accent="graphite"] {
      --accent: #475467;
      --accent-2: #0f766e;
    }

    * {
      box-sizing: border-box;
    }

    html,
    body {
      min-height: 100%;
      height: 100%;
      margin: 0;
    }

    body {
      background: linear-gradient(180deg, rgba(255, 255, 255, 0.4), rgba(255, 255, 255, 0)) fixed, var(--bg);
      color: var(--text);
      font-family: var(--ui-font);
      font-size: var(--app-font-size);
      letter-spacing: -0.01em;
      -webkit-tap-highlight-color: transparent;
    }

    html[data-theme="dark"] body {
      background: linear-gradient(180deg, rgba(255, 255, 255, 0.03), rgba(255, 255, 255, 0)) fixed, var(--bg);
    }

    button,
    input,
    textarea,
    select {
      font: inherit;
    }

    button {
      color: inherit;
    }

    .app-shell {
      min-height: 100dvh;
      display: flex;
      flex-direction: column;
    }

    .topbar {
      position: sticky;
      top: 0;
      z-index: 50;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
      min-height: calc(58px + env(safe-area-inset-top, 0px));
      padding-top: calc(8px + env(safe-area-inset-top, 0px));
      padding-bottom: 8px;
      padding-left: calc(clamp(12px, 2.5vw, 28px) + env(safe-area-inset-left, 0px));
      padding-right: calc(clamp(12px, 2.5vw, 28px) + env(safe-area-inset-right, 0px));
      background: color-mix(in srgb, var(--surface) 86%, transparent);
      border-bottom: 1px solid color-mix(in srgb, var(--line) 80%, transparent);
      backdrop-filter: blur(18px) saturate(180%);
      -webkit-backdrop-filter: blur(18px) saturate(180%);
      box-shadow: 0 1px 12px rgba(0, 0, 0, 0.03);
    }

    .brand {
      display: flex;
      align-items: center;
      gap: 10px;
      flex-shrink: 0;
      min-width: max-content;
      text-decoration: none;
      user-select: none;
      z-index: 2;
    }

    .brand-logo {
      width: clamp(30px, 3.2vw, 36px);
      height: clamp(30px, 3.2vw, 36px);
      border-radius: 9px;
      display: block;
      object-fit: contain;
      box-shadow: 0 3px 10px color-mix(in srgb, var(--accent) 25%, transparent);
      flex-shrink: 0;
      filter: drop-shadow(0 2px 4px rgba(0,0,0,0.12));
      transition: transform 0.22s cubic-bezier(0.34, 1.56, 0.64, 1), filter 0.2s ease, box-shadow 0.2s ease;
      border: 1px solid color-mix(in srgb, var(--line) 60%, transparent);
    }

    .brand:hover .brand-logo {
      transform: scale(1.05) rotate(-2deg);
      box-shadow: 0 6px 16px color-mix(in srgb, var(--accent) 35%, transparent);
    }

    html[data-theme="dark"] .brand-logo {
      filter: brightness(1.1) drop-shadow(0 2px 8px rgba(255,255,255,0.14));
      border-color: color-mix(in srgb, var(--line) 80%, transparent);
    }

    .sidebar-header .brand-logo {
      width: 32px;
      height: 32px;
    }

    .brand-text {
      min-width: max-content;
      display: flex;
      flex-direction: column;
      justify-content: center;
      flex-shrink: 0;
    }

    .brand-title {
      margin: 0;
      font-size: clamp(1.05rem, 1.6vw, 1.2rem);
      line-height: 1.15;
      font-weight: 800;
      letter-spacing: -0.02em;
      color: var(--text);
      white-space: nowrap;
    }

    .version-badge {
      font-size: 0.68rem;
      font-weight: 750;
      font-family: var(--ui-font);
      padding: 1.5px 7px;
      border-radius: 999px;
      background: var(--surface-3);
      color: var(--muted);
      border: 1px solid var(--line);
      line-height: 1.35;
      display: inline-flex;
      align-items: center;
      letter-spacing: 0.02em;
      white-space: nowrap;
    }

    .brand-subtitle {
      margin: 2px 0 0;
      color: var(--muted);
      font-size: 0.74rem;
      font-weight: 500;
      white-space: nowrap;
    }

    .top-nav {
      display: flex;
      align-items: center;
      gap: 3px;
      padding: 3px;
      background: color-mix(in srgb, var(--surface-2) 92%, var(--surface));
      border: 1px solid var(--line);
      border-radius: 10px;
      box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.03);
      flex-shrink: 0;
    }

    .top-nav-btn {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      padding: 0 clamp(8px, 1.1vw, 14px);
      min-height: 33px;
      border: none;
      border-radius: 7px;
      background: transparent;
      color: var(--muted);
      font-size: 0.83rem;
      font-weight: 650;
      cursor: pointer;
      white-space: nowrap;
      transition: all 0.18s cubic-bezier(0.16, 1, 0.3, 1);
      user-select: none;
      flex-shrink: 0;
    }

    .top-nav-btn:hover {
      color: var(--text);
      background: color-mix(in srgb, var(--surface) 60%, transparent);
      transform: translateY(-1px);
    }

    .top-nav-btn:active {
      transform: scale(0.96);
    }

    .top-nav-btn.active {
      background: var(--surface);
      color: var(--accent);
      font-weight: 750;
      box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.04);
    }


    .toolbar,
    .inline-actions,
    .segmented,
    .presentation-controls,
    .export-grid {
      display: flex;
      align-items: center;
      gap: 6px;
      flex-wrap: wrap;
    }

    /* Desktop top-actions: compact horizontal strip */
    .top-actions {
      display: flex;
      align-items: center;
      gap: 7px;
      flex-wrap: nowrap;
      flex-shrink: 0;
    }

    #topbarProfileContainer {
      display: flex;
      align-items: center;
      gap: 7px;
      padding: 3px 10px 3px 4px;
      background: var(--surface-2);
      border: 1px solid var(--line);
      border-radius: 999px;
      transition: all 0.18s cubic-bezier(0.16, 1, 0.3, 1);
      cursor: pointer;
      user-select: none;
    }

    #topbarProfileContainer:hover {
      background: var(--surface-3);
      border-color: color-mix(in srgb, var(--accent) 35%, var(--line));
      transform: translateY(-1px);
    }

    #topbarUserAvatar {
      width: 26px;
      height: 26px;
      border-radius: 50%;
      object-fit: cover;
      border: 1.5px solid var(--surface);
      box-shadow: 0 1px 4px rgba(0, 0, 0, 0.1);
    }

    #topbarUserGreeting {
      font-size: 0.8rem;
      font-weight: 650;
      color: var(--text);
      letter-spacing: -0.01em;
    }

    /* Hamburger toggle — visible across all devices to open sidebar drawer */
    .topbar-menu-btn {
      display: inline-flex;
      flex-shrink: 0;
      width: 38px;
      height: 38px;
      padding: 0;
      align-items: center;
      justify-content: center;
      border-radius: 8px;
      border: 1px solid var(--line);
      background: var(--surface-2);
      color: var(--text);
      cursor: pointer;
      transition: all 0.16s cubic-bezier(0.16, 1, 0.3, 1);
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.03);
    }


    .topbar-menu-btn:hover {
      background: var(--surface-3);
      border-color: color-mix(in srgb, var(--accent) 35%, var(--line));
      transform: translateY(-1px);
    }

    .topbar-menu-btn:active {
      transform: scale(0.94);
    }

    .topbar-menu-btn svg {
      width: 18px;
      height: 18px;
      stroke-width: 2.2;
    }

    /* Mobile quick actions (theme + present) — hidden on desktop */
    .topbar-mobile-actions {
      display: none;
      align-items: center;
      gap: 7px;
      flex-shrink: 0;
    }

    #mobileUserAvatar {
      width: 28px;
      height: 28px;
      border-radius: 50%;
      object-fit: cover;
      cursor: pointer;
      border: 1.5px solid var(--line);
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
      transition: transform 0.15s ease, border-color 0.15s ease;
    }

    #mobileUserAvatar:hover {
      transform: scale(1.05);
      border-color: var(--accent);
    }

    #themeToggleMobile {
      width: 36px;
      height: 36px;
      border-radius: 8px;
      border: 1px solid var(--line);
      background: var(--surface-2);
    }


    /* Full-width utility for sidebar buttons */
    .button.full-width {
      width: 100%;
      justify-content: flex-start;
    }

    /* Compact button variant */
    .button.compact {
      padding: 0 10px;
      min-height: 30px;
      font-size: 0.8rem;
    }

    /* ─── Sidebar backdrop ─── */
    .sidebar-backdrop {
      display: none;
      position: fixed;
      inset: 0;
      background: rgba(0, 0, 0, 0.45);
      z-index: 98;
      opacity: 0;
      transition: opacity 0.25s ease;
    }
    .sidebar-backdrop.open {
      display: block;
      opacity: 1;
    }

    /* ─── Sidebar drawer ─── */
    .sidebar-drawer {
      position: fixed;
      top: 0;
      left: 0;
      height: 100%;
      width: 280px;
      max-width: 85vw;
      background: var(--surface);
      border-right: 1px solid var(--line);
      box-shadow: 4px 0 24px rgba(0,0,0,0.15);
      z-index: 99;
      display: flex;
      flex-direction: column;
      transform: translateX(-100%);
      transition: transform 0.28s cubic-bezier(0.4, 0, 0.2, 1);
      overflow-y: auto;
      overscroll-behavior: contain;
      padding-bottom: calc(24px + env(safe-area-inset-bottom, 0px));
    }
    .sidebar-drawer.open {
      transform: translateX(0);
    }

    .sidebar-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 16px 16px calc(16px + env(safe-area-inset-top, 0px));
      padding-top: calc(16px + env(safe-area-inset-top, 0px));
      border-bottom: 1px solid var(--line);
      flex-shrink: 0;
    }

    .sidebar-nav {
      display: flex;
      flex-direction: column;
      padding: 10px 10px;
      gap: 4px;
    }

    .sidebar-nav-btn {
      display: inline-flex;
      align-items: center;
      gap: 10px;
      padding: 10px 14px;
      border: none;
      border-radius: 8px;
      background: transparent;
      color: var(--text);
      font-size: 0.92rem;
      font-weight: 600;
      cursor: pointer;
      text-align: left;
      transition: background 0.15s ease, color 0.15s ease;
      width: 100%;
    }
    .sidebar-nav-btn:hover {
      background: var(--surface-2);
    }
    .sidebar-nav-btn.active {
      background: color-mix(in srgb, var(--accent) 15%, var(--surface-2));
      color: var(--accent);
    }
    .sidebar-nav-btn::before {
      content: attr(data-icon-char);
    }

    .sidebar-divider {
      height: 1px;
      background: var(--line);
      margin: 4px 0;
      flex-shrink: 0;
    }

    .sidebar-actions {
      display: flex;
      flex-direction: column;
      padding: 10px;
      gap: 6px;
    }

    .sidebar-footer {
      display: flex;
      flex-direction: column;
      gap: 8px;
      padding: 12px;
    }

    .sidebar-label {
      font-size: 0.75rem;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.06em;
      color: var(--muted);
    }

    .mobile-view-switcher {
      display: none;
      padding: 8px 12px calc(8px + env(safe-area-inset-bottom, 0px)); min-height: calc(66px + env(safe-area-inset-bottom, 0px));
      gap: 6px;
      grid-template-columns: repeat(5, minmax(0, 1fr));
      position: fixed;
      bottom: 0;
      left: 0;
      right: 0;
      background: color-mix(in srgb, var(--surface) 92%, transparent);
      backdrop-filter: blur(14px);
      -webkit-backdrop-filter: blur(14px);
      border-top: 1px solid var(--line);
      z-index: 60;
    }

    .workspace {
      display: flex;
      flex-direction: column;
      gap: 12px;
      width: 100%;
      max-width: 1400px;
      margin: 0 auto;
      padding: 14px clamp(12px, 2vw, 24px);
      flex: 1;
      min-height: 0;
    }

    .panel {
      background: var(--surface);
      border: 1px solid var(--line);
      border-radius: var(--radius);
      min-width: 0;
      box-shadow: 0 1px 4px rgba(0, 0, 0, 0.04);
      display: none;
      flex-direction: column;
      flex: 1;
      min-height: 0;
      animation: viewFadeIn 0.22s cubic-bezier(0.16, 1, 0.3, 1);
    }

    @keyframes viewFadeIn {
      from {
        opacity: 0;
        transform: translateY(6px);
      }
      to {
        opacity: 1;
        transform: translateY(0);
      }
    }

    .workspace[data-view="editor"] > .editor-panel,
    .workspace[data-view="library"] > .library-panel,
    .workspace[data-view="tools"] > .tools-panel,
    .workspace[data-view="theory"] > .theory-panel,
    .workspace[data-view="instruments"] > .instrument-panel,
    .workspace[data-view="about"] > .about-panel {
      display: flex !important;
    }

    .library-panel,
    .tools-panel,
    .theory-panel,
    .instrument-panel,
    .about-panel {
      padding: var(--panel-pad);
      gap: 14px;
    }

    .editor-panel {
      min-height: 60dvh;
      overflow: hidden;
    }

    .editor-split-container {
      display: grid;
      grid-template-columns: minmax(320px, 1fr) minmax(360px, 1.25fr);
      gap: 16px;
      flex: 1;
      min-height: 0;
      padding: 12px 14px;
      background: var(--surface);
    }

    .editor-pane-left,
    .editor-pane-right {
      display: flex;
      flex-direction: column;
      min-height: 0;
      border: 1px solid var(--line);
      border-radius: var(--radius);
      background: var(--surface-2);
      overflow: hidden;
    }

    .pane-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 8px 12px;
      border-bottom: 1px solid var(--line);
      background: var(--surface);
    }

    .pane-tag {
      font-size: 0.72rem;
      font-weight: 750;
      color: var(--muted);
      letter-spacing: 0.05em;
    }

    .editor-pane-left .editor-container {
      flex: 1;
      min-height: 0;
      background: var(--surface-2);
    }

    .editor-pane-left .textarea {
      flex: 1;
      height: 100%;
      min-height: 0;
      background: transparent;
      padding: 14px 18px;
    }

    .editor-pane-right .preview-output {
      flex: 1;
      min-height: 0;
      overflow-y: auto;
      padding: 16px 20px;
      font-size: var(--preview-font);
      line-height: 1.55;
      white-space: pre;
      background: var(--surface-2);
    }

    .tools-grid-layout {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
      gap: 16px;
      width: 100%;
    }

    .tool-dashboard-card {
      background: var(--surface-2);
      border: 1px solid var(--line);
      border-radius: var(--radius);
      padding: 16px;
      display: flex;
      flex-direction: column;
      gap: 14px;
    }

    .panel-heading {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 10px;
      margin-bottom: 4px;
    }

    .panel-heading h2,
    .section-title {
      display: flex;
      align-items: center;
      gap: 6px;
      margin: 0;
      font-size: 0.88rem;
      line-height: 1.2;
      font-weight: 720;
      color: var(--text);
    }

    .section-title {
      padding-top: 6px;
    }

    .help-icon {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      width: 18px;
      height: 18px;
      border-radius: 50%;
      background: var(--surface-3);
      color: var(--text);
      font-size: 11px;
      font-weight: bold;
      cursor: pointer;
      transition: all 0.2s;
      border: 1px solid var(--line);
      flex-shrink: 0;
      text-decoration: none;
    }

    .help-icon:hover {
      background: var(--accent);
      color: white;
      border-color: var(--accent);
    }

    .help-popover {
      position: fixed;
      width: max-content;
      max-width: 280px;
      padding: 12px 16px;
      background: var(--text);
      color: var(--bg);
      font-size: 0.85rem;
      border-radius: 8px;
      box-shadow: 0 12px 32px rgba(0, 0, 0, 0.3);
      z-index: 999999;
      animation: popIn 0.15s cubic-bezier(0.175, 0.885, 0.32, 1.275);
      line-height: 1.5;
      pointer-events: none;
      text-align: left;
    }

    @keyframes popIn {
      from {
        opacity: 0;
        transform: translateY(-8px) scale(0.95);
      }

      to {
        opacity: 1;
        transform: translateY(0) scale(1);
      }
    }

    .field,
    .settings-field {
      display: grid;
      gap: 6px;
    }

    .field label,
    .settings-field label,
    .control-label {
      display: flex;
      align-items: center;
      gap: 6px;
      color: var(--muted);
      font-size: 0.78rem;
      font-weight: 650;
    }

    .input,
    .select,
    .textarea {
      width: 100%;
      border: 1px solid var(--line);
      border-radius: 6px;
      background: var(--surface-2);
      color: var(--text);
      outline: none;
      transition: border-color 140ms ease, box-shadow 140ms ease;
    }

    .input,
    .select {
      height: 36px;
      padding: 0 10px;
      font-size: 0.88rem;
    }

    .textarea {
      min-height: 300px;
      resize: none;
      border: 0;
      border-radius: 0;
      padding: 16px;
      background: transparent;
      font-family: var(--chart-font);
      font-size: var(--editor-font);
      line-height: var(--editor-line);
      white-space: pre-wrap;
      overflow: auto;
      tab-size: 4;
      z-index: 2;
      position: relative;
    }

    .editor-container {
      position: relative;
      flex: 1;
      display: flex;
      flex-direction: column;
      min-height: 0;
      background: var(--surface);
    }

    .editor-placeholder {
      position: absolute;
      inset: 0;
      padding: 32px;
      pointer-events: none;
      color: var(--muted);
      font-family: var(--ui-font);
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
      text-align: center;
      opacity: 0;
      transition: opacity 0.2s;
      z-index: 1;
      background: var(--surface);
      overflow-y: auto;
    }

    .textarea:placeholder-shown~.editor-placeholder {
      opacity: 1;
      pointer-events: auto;
      cursor: text;
    }

    .textarea:focus~.editor-placeholder {
      opacity: 0 !important;
      pointer-events: none !important;
    }

    .editor-placeholder h3 {
      margin: 0 0 12px;
      color: var(--text);
      font-size: 1.35rem;
      font-weight: 700;
    }

    .editor-placeholder p {
      font-size: 0.95rem;
      margin: 0 0 16px;
      max-width: 420px;
      line-height: 1.5;
    }

    .editor-placeholder ul {
      text-align: left;
      font-size: 0.9rem;
      line-height: 1.8;
      margin: 0 auto;
      padding: 0;
      list-style: none;
      max-width: 320px;
    }

    .editor-placeholder li {
      margin-bottom: 8px;
      display: flex;
      align-items: center;
      gap: 10px;
    }

    .editor-placeholder code {
      background: var(--surface-2);
      padding: 4px 8px;
      border-radius: 4px;
      font-family: var(--chart-font);
      font-size: 0.85em;
      color: var(--accent);
      font-weight: bold;
      min-width: 50px;
      text-align: center;
      border: 1px solid var(--line);
    }

    .input:focus,
    .select:focus,
    .textarea:focus {
      border-color: var(--accent);
      box-shadow: 0 0 0 2px color-mix(in srgb, var(--accent) 18%, transparent);
    }

    .textarea:focus {
      box-shadow: inset 0 0 0 2px color-mix(in srgb, var(--accent) 30%, transparent);
    }

    .input:read-only,
    .textarea:read-only {
      opacity: 0.85;
      background: var(--surface-3);
      cursor: not-allowed;
    }

    .song-title-input:read-only {
      background: var(--surface);
      cursor: default;
    }

    .song-title-input {
      height: auto;
      min-height: 46px;
      padding: 12px 18px 6px;
      border: 0;
      border-radius: 0;
      background: var(--surface);
      color: var(--text);
      font-size: clamp(1.15rem, 2.5vw, 1.65rem);
      line-height: 1.25;
      font-weight: 700;
      letter-spacing: -0.01em;
    }

    .song-title-input:focus {
      box-shadow: none;
    }

    .editor-toolbar {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 10px;
      padding: 8px 14px 10px;
      border-bottom: 1px solid var(--line);
      background: var(--surface);
    }

    .status-line {
      min-height: 20px;
      color: var(--muted);
      font-size: 0.75rem;
      white-space: nowrap;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .badge {
      padding: 2px 6px;
      background: var(--warning);
      color: #fff;
      border-radius: 4px;
      font-size: 0.65rem;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.05em;
    }

    .setlist-nav {
      display: none;
      align-items: center;
      justify-content: space-between;
      padding: 8px 14px;
      background: color-mix(in srgb, var(--accent) 12%, var(--surface));
      border-bottom: 1px solid var(--line);
      font-size: 0.88rem;
    }

    .button,
    .icon-button,
    .tab-button {
      border: 1px solid var(--line);
      border-radius: 6px;
      background: var(--surface-2);
      color: var(--text);
      min-height: 34px;
      padding: 0 12px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      font-size: 0.85rem;
      font-weight: 600;
      text-decoration: none;
      transition: all 0.15s cubic-bezier(0.4, 0, 0.2, 1);
      user-select: none;
    }

    .button:hover,
    .icon-button:hover {
      border-color: color-mix(in srgb, var(--accent) 35%, var(--line));
      transform: translateY(-1px);
      box-shadow: 0 2px 6px rgba(0, 0, 0, 0.06);
    }

    .button:active,
    .icon-button:active,
    .tab-button:active {
      transform: scale(0.96) translateY(0);
    }

    .icon-button {
      width: var(--tap-size);
      min-height: var(--tap-size);
      padding: 0;
    }

    .icon {
      width: 16px;
      height: 16px;
      flex: 0 0 auto;
      stroke-width: 2.2;
    }

    .button-label {
      min-width: 0;
      overflow: hidden;
      text-overflow: ellipsis;
      white-space: nowrap;
    }

    .button.primary {
      background: var(--accent);
      border-color: var(--accent);
      color: #fff;
      box-shadow: 0 2px 8px color-mix(in srgb, var(--accent) 28%, transparent);
    }

    .button.primary:hover {
      filter: brightness(1.06);
      box-shadow: 0 4px 12px color-mix(in srgb, var(--accent) 40%, transparent);
      transform: translateY(-1px);
    }

    .button.secondary {
      background: color-mix(in srgb, var(--accent) 8%, var(--surface));
      border-color: color-mix(in srgb, var(--accent) 25%, var(--line));
      color: var(--accent);
    }

    .button.secondary:hover {
      background: color-mix(in srgb, var(--accent) 14%, var(--surface));
    }

    .button.danger,
    .icon-button.danger {
      color: var(--danger);
      border-color: color-mix(in srgb, var(--danger) 25%, var(--line));
      background: color-mix(in srgb, var(--danger) 8%, var(--surface));
    }

    .button.danger:hover,
    .icon-button.danger:hover {
      background: color-mix(in srgb, var(--danger) 16%, var(--surface));
      border-color: var(--danger);
    }

    .button.ghost,
    .icon-button.ghost {
      background: transparent;
      border-color: transparent;
      box-shadow: none;
    }

    .button.ghost:hover,
    .icon-button.ghost:hover {
      background: var(--surface-2);
      border-color: var(--line);
    }

    .segmented {
      padding: 4px;
      border: 1px solid var(--line);
      border-radius: 8px;
      background: var(--surface-2);
      display: inline-flex;
      gap: 2px;
    }

    .tab-button {
      border: 0;
      min-height: 30px;
      padding: 0 12px;
      background: transparent;
      color: var(--muted);
      font-size: 0.8rem;
      font-weight: 600;
      flex-direction: column;
      gap: 2px;
      border-radius: 6px;
      box-shadow: none;
    }

    .tab-button:hover {
      color: var(--text);
      background: color-mix(in srgb, var(--surface) 60%, transparent);
    }

    .tab-button.active {
      background: var(--surface);
      color: var(--accent);
      font-weight: 750;
      box-shadow: 0 1px 4px rgba(16, 24, 40, 0.08);
    }

    .library-list {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
      grid-auto-rows: max-content;
      gap: 12px;
      overflow-y: auto;
      overflow-x: hidden;
      flex: 1;
      align-content: start;
      align-items: start;
      min-height: 320px;
      padding: 4px 2px 24px;
    }

    .song-card {
      border: 1px solid var(--line);
      border-radius: 10px;
      background: var(--surface);
      padding: 14px 16px;
      min-height: 68px;
      display: grid;
      grid-template-columns: minmax(0, 1fr) auto;
      gap: 12px;
      align-items: center;
      cursor: pointer;
      text-align: left;
      transition: all 0.15s cubic-bezier(0.4, 0, 0.2, 1);
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
    }

    .song-card:hover {
      border-color: color-mix(in srgb, var(--accent) 40%, var(--line));
      transform: translateY(-2px);
      box-shadow: 0 4px 12px rgba(0, 0, 0, 0.06);
    }

    .song-card:active {
      transform: scale(0.98);
    }

    .song-card.active {
      border-color: var(--accent);
      background: color-mix(in srgb, var(--accent) 8%, var(--surface));
      box-shadow: 0 2px 8px color-mix(in srgb, var(--accent) 18%, transparent);
    }

    .song-card-title {
      margin: 0;
      font-size: 0.92rem;
      font-weight: 700;
      overflow: hidden;
      text-overflow: ellipsis;
      white-space: nowrap;
      display: flex;
      align-items: center;
      gap: 6px;
      color: var(--text);
    }

    .song-card-meta {
      margin: 4px 0 0;
      color: var(--muted);
      font-size: 0.76rem;
      overflow: hidden;
      text-overflow: ellipsis;
      white-space: nowrap;
    }

    .empty-state {
      border: 1px dashed var(--line);
      border-radius: 8px;
      padding: 24px;
      text-align: center;
      color: var(--muted);
      background: var(--surface-2);
      font-size: 0.85rem;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 10px;
    }

    .metric-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
    }

    .metric {
      border: 1px solid var(--line);
      border-radius: 6px;
      padding: 10px;
      background: var(--surface-2);
      min-width: 0;
    }

    .metric span {
      display: block;
      color: var(--muted);
      font-size: 0.72rem;
      font-weight: 650;
      margin-bottom: 2px;
    }

    .metric strong {
      display: block;
      font-size: 0.9rem;
      font-weight: 700;
      line-height: 1.2;
      overflow: hidden;
      text-overflow: ellipsis;
      white-space: nowrap;
    }

    .tool-card {
      display: grid;
      gap: 12px;
      border: 1px solid var(--line);
      border-radius: 8px;
      padding: 12px;
      background: var(--surface-2);
    }

    .tool-card-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
    }

    .tool-card-title {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      min-width: 0;
      font-size: 0.85rem;
      font-weight: 700;
    }

    .tool-card-value {
      color: var(--muted);
      font-size: 0.78rem;
      font-variant-numeric: tabular-nums;
      white-space: nowrap;
    }

    .beat-row {
      display: grid;
      grid-template-columns: repeat(4, minmax(0, 1fr));
      gap: 4px;
    }

    .beat-dot {
      height: 8px;
      border-radius: 999px;
      background: var(--surface);
      border: 1px solid var(--line);
      transition: background 90ms ease, transform 90ms ease;
    }

    .beat-dot.active {
      background: var(--accent);
      border-color: var(--accent);
      transform: scaleY(1.3);
    }

    .beat-dot.downbeat {
      background: var(--accent-2);
      border-color: var(--accent-2);
    }

    .preview-card {
      display: flex;
      flex-direction: column;
      min-height: 240px;
      overflow: hidden;
      border: 1px solid var(--line);
      border-radius: 8px;
      background: var(--surface-2);
    }

    .preview-header {
      padding: 10px;
      border-bottom: 1px solid var(--line);
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
      overflow-x: auto;
      scrollbar-width: none;
    }

    .preview-output {
      margin: 0;
      padding: 12px;
      overflow: auto;
      flex: 1;
      color: var(--text);
      font-family: var(--chart-font);
      font-size: var(--preview-font);
      line-height: 1.5;
      white-space: pre;
      tab-size: 4;
    }

    .export-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
    }

    .export-grid .button {
      width: 100%;
    }

    .layout-row {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 8px;
    }

    .circle-container {
      position: relative;
      width: 100%;
      max-width: 400px;
      aspect-ratio: 1/1;
      margin: 0 auto;
      border-radius: 50%;
      overflow: hidden;
      box-shadow: 0 4px 20px rgba(0, 0, 0, 0.06);
    }

    .explanation-text {
      color: var(--muted);
      font-size: 0.82rem;
      line-height: 1.45;
      margin-top: 12px;
      background: var(--surface-2);
      padding: 12px;
      border-radius: 8px;
      border-left: 3px solid var(--accent);
    }

    .piano-container {
      width: 100%;
      overflow-x: auto;
      padding: 14px 16px 20px;
      -webkit-overflow-scrolling: touch;
      border: 1px solid var(--line);
      border-radius: 12px;
      background: var(--surface-2);
      margin-bottom: 8px;
      scrollbar-width: thin;
      scrollbar-color: var(--subtle) var(--surface-3);
      box-shadow: inset 0 2px 6px rgba(0, 0, 0, 0.05);
    }

    .piano-container::-webkit-scrollbar,
    .fretboard-container::-webkit-scrollbar {
      height: 10px;
      -webkit-appearance: none;
      display: block;
    }

    .piano-container::-webkit-scrollbar-track,
    .fretboard-container::-webkit-scrollbar-track {
      background: var(--surface-3);
      border-radius: 6px;
    }

    .piano-container::-webkit-scrollbar-thumb,
    .fretboard-container::-webkit-scrollbar-thumb {
      background: var(--subtle);
      border-radius: 6px;
      border: 2px solid var(--surface-3);
    }

    .piano-scroll {
      display: flex;
      height: 175px;
      padding: 0 8px;
      width: 100%;
      min-width: max-content;
      justify-content: center;
      background: #141414;
      border-radius: 8px 8px 10px 10px;
      box-shadow: 0 8px 24px rgba(0, 0, 0, 0.25), inset 0 2px 4px rgba(255, 255, 255, 0.15);
      border: 3px solid #222;
    }

    .piano-key {
      position: relative;
      border-radius: 0 0 6px 6px;
      cursor: pointer;
      user-select: none;
      transition: all 0.08s ease;
    }

    .piano-key-white {
      background: linear-gradient(to bottom, #fcfcfc 0%, #f4f4f4 80%, #ebebeb 100%);
      border: 1px solid #d0d0d0;
      border-top: none;
      width: clamp(48px, 4.5vw, 64px);
      height: 100%;
      z-index: 1;
      margin-right: -1px;
      display: flex;
      align-items: flex-end;
      justify-content: center;
      padding-bottom: 12px;
      box-shadow: inset 0 -5px 8px rgba(0, 0, 0, 0.08), 0 2px 3px rgba(0, 0, 0, 0.12);
    }

    .piano-key-white:hover {
      background: linear-gradient(to bottom, #ffffff 0%, #f9f9f9 80%, #f0f0f0 100%);
    }

    .piano-key-white .key-label {
      font-size: 0.85rem;
      color: #333;
      font-weight: 750;
      pointer-events: none;
      font-family: var(--ui-font);
    }

    .piano-key-black {
      background: linear-gradient(to bottom, #2d2d2d 0%, #1a1a1a 75%, #0d0d0d 100%);
      width: clamp(30px, 2.8vw, 40px);
      height: 60%;
      z-index: 2;
      margin-left: clamp(-15px, -1.4vw, -20px);
      margin-right: clamp(-15px, -1.4vw, -20px);
      border: 1px solid #000;
      border-top: none;
      border-radius: 0 0 4px 4px;
      display: flex;
      align-items: flex-end;
      justify-content: center;
      padding-bottom: 10px;
      box-shadow: 0 4px 8px rgba(0, 0, 0, 0.6), inset 0 1px 2px rgba(255, 255, 255, 0.25), inset 0 -3px 4px rgba(0, 0, 0, 0.8);
    }

    .piano-key-black .key-label {
      font-size: 0.72rem;
      color: #eee;
      font-weight: 700;
      pointer-events: none;
      text-align: center;
      line-height: 1.1;
      font-family: var(--ui-font);
    }

    .piano-key-white:active,
    .piano-key-white.active {
      background: linear-gradient(to bottom, var(--accent) 0%, color-mix(in srgb, var(--accent) 80%, black) 100%) !important;
      box-shadow: inset 0 2px 6px rgba(0, 0, 0, 0.3) !important;
      transform: translateY(2px);
    }

    .piano-key-white:active .key-label,
    .piano-key-white.active .key-label {
      color: #fff !important;
    }

    .piano-key-black:active,
    .piano-key-black.active {
      background: linear-gradient(to bottom, var(--accent-2) 0%, color-mix(in srgb, var(--accent-2) 75%, black) 100%) !important;
      box-shadow: inset 0 2px 6px rgba(0, 0, 0, 0.5) !important;
      transform: translateY(2px);
    }

    /* ── Scale highlight on piano keys (Pastel Green & Darker Green Root) ── */
    .piano-key-white.key-root {
      background: linear-gradient(to bottom, #16a34a 0%, #15803d 100%) !important;
      box-shadow: inset 0 -4px 0 #14532d !important;
    }
    .piano-key-white.key-root .key-label {
      color: #ffffff !important;
      font-weight: 800 !important;
    }

    .piano-key-white.key-in-scale {
      background: linear-gradient(to bottom, #dcfce7 0%, #bbf7d0 100%) !important;
      box-shadow: inset 0 -3px 0 #86efac !important;
    }
    .piano-key-white.key-in-scale .key-label {
      color: #14532d !important;
      font-weight: 750 !important;
    }

    .piano-key-black.key-root {
      background: linear-gradient(to bottom, #15803d 0%, #052e16 100%) !important;
      border: 1.5px solid #22c55e !important;
      box-shadow: 0 0 10px rgba(34, 197, 94, 0.45) !important;
    }
    .piano-key-black.key-root .key-label {
      color: #ffffff !important;
      font-weight: 800 !important;
      text-shadow: 0 1px 2px rgba(0,0,0,0.8);
    }

    .piano-key-black.key-in-scale {
      background: linear-gradient(to bottom, #064e3b 0%, #022c22 100%) !important;
      border: 1px solid #10b981 !important;
    }
    .piano-key-black.key-in-scale .key-label {
      color: #86efac !important;
      font-weight: 750 !important;
    }

    /* Playback always overrides scale highlight */
    .piano-key-white.active, .piano-key-white:active {
      background: linear-gradient(to bottom, var(--accent) 0%, color-mix(in srgb, var(--accent) 80%, black) 100%) !important;
    }
    .piano-key-white.active .key-label, .piano-key-white:active .key-label {
      color: #ffffff !important;
    }

    /* ── Scale highlight on fret cells ── */
    .fret-cell.fret-root .fret-note-marker {
      background: #15803d !important;
      color: #ffffff !important;
      opacity: 1 !important;
      font-weight: 800 !important;
      box-shadow: 0 0 0 2px #4ade80, 0 2px 8px rgba(21, 128, 61, 0.6) !important;
    }
    .fret-cell.fret-in-scale .fret-note-marker {
      background: #86efac !important;
      color: #14532d !important;
      opacity: 1 !important;
      font-weight: 750 !important;
      border: 1px solid #4ade80 !important;
    }

    html[data-theme="dark"] .fret-cell.fret-in-scale .fret-note-marker {
      background: #064e3b !important;
      color: #86efac !important;
      border: 1px solid #16a34a !important;
    }



    .fretboard-container {
      width: 100%;
      overflow-x: auto;
      padding: 14px 16px 20px;
      -webkit-overflow-scrolling: touch;
      border: 1px solid var(--line);
      border-radius: 12px;
      background: var(--surface-2);
      margin-bottom: 8px;
      scrollbar-width: thin;
      scrollbar-color: var(--subtle) var(--surface-3);
      box-shadow: inset 0 2px 6px rgba(0, 0, 0, 0.05);
    }

    .fretboard {
      display: flex;
      flex-direction: column;
      width: 100%;
      min-width: 860px;
      padding: 0;
      background: linear-gradient(180deg, #20110a 0%, #351c12 30%, #402317 50%, #351c12 70%, #20110a 100%);
      border-radius: 6px;
      border: 3px solid #1a0b06;
      box-shadow: 0 8px 24px rgba(0, 0, 0, 0.3), inset 0 0 16px rgba(0, 0, 0, 0.7);
      position: relative;
      user-select: none;
    }

    .fret-string {
      display: flex;
      position: relative;
      height: 38px;
      align-items: center;
      width: 100%;
    }

    .fret-string::before {
      content: '';
      position: absolute;
      left: 0;
      right: 0;
      height: var(--string-gauge, 2px);
      background: var(--string-color, linear-gradient(to bottom, #f0f0f0, #888));
      z-index: 2;
      pointer-events: none;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.6);
    }

    .fret-cell {
      height: 100%;
      border-right: 3px solid #8d98a5;
      box-shadow: inset -1px 0 1px rgba(255, 255, 255, 0.4), 1px 0 2px rgba(0, 0, 0, 0.6);
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      cursor: pointer;
      transition: background 0.12s;
    }

    .fret-cell:hover {
      background: rgba(255, 255, 255, 0.06);
    }

    .fret-cell:first-child {
      flex: 0 0 44px !important;
      width: 44px !important;
      background: linear-gradient(to right, #e8e4db 0%, #dcd6c8 70%, #c4bcae 100%);
      border-right: 6px solid #b0a696;
      box-shadow: 2px 0 6px rgba(0, 0, 0, 0.5);
    }

    .fret-dot {
      position: absolute;
      width: 15px;
      height: 15px;
      border-radius: 50%;
      background: radial-gradient(circle, #ffffff 20%, #e0e4e8 70%, #a8b0b8 100%);
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.6), inset 0 1px 1px rgba(255, 255, 255, 0.8);
      pointer-events: none;
      z-index: 1;
      opacity: 0.85;
    }

    .fret-note-marker {
      position: relative;
      z-index: 3;
      width: 28px;
      height: 28px;
      border-radius: 50%;
      background: var(--accent);
      color: white;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 0.75rem;
      font-weight: 800;
      opacity: 0;
      transform: scale(0.7);
      transition: all 0.15s cubic-bezier(0.175, 0.885, 0.32, 1.275);
      pointer-events: none;
      box-shadow: 0 3px 8px rgba(0, 0, 0, 0.4), 0 0 0 2px rgba(255, 255, 255, 0.4);
    }

    .fret-cell:active .fret-note-marker,
    .fret-cell.active .fret-note-marker {
      opacity: 1;
      transform: scale(1);
    }

    .modal-host {
      position: fixed;
      inset: 0;
      z-index: 200;
      display: flex;
      align-items: center;
      justify-content: center;
      padding: calc(14px + env(safe-area-inset-top, 0px)) calc(14px + env(safe-area-inset-right, 0px)) calc(14px + env(safe-area-inset-bottom, 0px)) calc(14px + env(safe-area-inset-left, 0px));
    }

    .modal-host[hidden] {
      display: none;
    }

    .modal-backdrop {
      position: absolute;
      inset: 0;
      background: rgba(4, 8, 16, 0.55);
      backdrop-filter: blur(8px);
      -webkit-backdrop-filter: blur(8px);
    }

    .modal {
      position: relative;
      width: min(600px, 100%);
      max-height: 100%;
      display: flex;
      flex-direction: column;
      margin: 0;
      padding: 0;
      border-radius: 12px;
      border: 1px solid var(--line);
      background: var(--surface);
      box-shadow: var(--shadow);
      animation: modalFade 0.2s ease-out;
    }

    @keyframes modalFade {
      from {
        opacity: 0;
        transform: translateY(12px) scale(0.98);
      }

      to {
        opacity: 1;
        transform: translateY(0) scale(1);
      }
    }

    .modal-header {
      padding: 18px 24px 12px;
      flex-shrink: 0;
    }

    .modal-header h2 {
      margin: 0 0 6px;
      font-size: 1.1rem;
      line-height: 1.2;
      font-weight: 760;
      display: flex;
      align-items: center;
      gap: 8px;
    }

    .modal-message {
      margin: 0;
      color: var(--muted);
      font-size: 0.88rem;
      line-height: 1.45;
    }

    .modal-fields {
      padding: 8px clamp(12px, 3vw, 24px) 20px;
      overflow-y: auto;
      -webkit-overflow-scrolling: touch;
      display: flex;
      flex-direction: column;
      gap: 12px;
      flex: 1;
      min-height: 0;
    }

    .modal-fields table {
      width: 100%;
      border-collapse: collapse;
      font-size: 0.85rem;
    }


    .modal-actions {
      padding: 14px 24px;
      flex-shrink: 0;
      display: flex;
      justify-content: flex-end;
      gap: 8px;
      flex-wrap: wrap;
      border-top: 1px solid var(--line);
      background: color-mix(in srgb, var(--surface) 95%, transparent);
      border-radius: 0 0 12px 12px;
    }

    .range-row {
      display: grid;
      grid-template-columns: minmax(0, 1fr) 60px;
      gap: 10px;
      align-items: center;
    }

    input[type="range"] {
      accent-color: var(--accent);
      width: 100%;
      cursor: pointer;
    }

    .range-value {
      color: var(--muted);
      font-size: 0.8rem;
      text-align: right;
      font-variant-numeric: tabular-nums;
    }

    .settings-heading {
      margin-top: 6px;
      padding-top: 10px;
      border-top: 1px solid var(--line);
      color: var(--text);
      font-size: 0.85rem;
      font-weight: 760;
    }

    .toast-host {
      position: fixed;
      right: 16px;
      z-index: 300;
      display: grid;
      gap: 8px;
      width: min(340px, calc(100vw - 32px));
      pointer-events: none;
      bottom: 16px;
      transition: bottom 0.2s;
    }

    .toast {
      padding: 12px 16px;
      border-radius: 8px;
      background: var(--surface);
      color: var(--text);
      border: 1px solid var(--line);
      box-shadow: 0 12px 32px rgba(0, 0, 0, 0.15);
      font-size: 0.88rem;
      font-weight: 600;
      transition: all 0.3s ease;
      display: flex;
      align-items: center;
      gap: 10px;
    }

    .presentation[data-pres-theme="light"] {
      --p-bg: #f6f7f9;
      --p-text: #16181d;
      --p-surface: #ffffff;
      --p-line: #d8dde6;
      --p-muted: #667085;
      --p-accent: var(--accent, #1967d2);
      --p-slash: var(--warning-slash, #e65100);
    }

    .presentation[data-pres-theme="dark"] {
      --p-bg: #0f1115;
      --p-text: #f1f5f9;
      --p-surface: #17191f;
      --p-line: #334155;
      --p-muted: #94a3b8;
      --p-accent: var(--accent, #60a5fa);
      --p-slash: var(--warning-slash, #fbbf24);
    }

    .presentation[data-pres-theme="stage"] {
      --p-bg: #000000;
      --p-text: #ffffff;
      --p-surface: #111111;
      --p-line: #333333;
      --p-muted: #888888;
      --p-accent: var(--accent, #3b82f6);
      --p-slash: var(--warning-slash, #f59e0b);
    }

    .presentation {
      position: fixed;
      inset: 0;
      z-index: 500;
      display: flex;
      flex-direction: column;
      background: var(--p-bg);
      color: var(--p-text);
      transition: background 0.3s;
    }

    .presentation[hidden] {
      display: none;
    }

    .presentation-top {
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      z-index: 510;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
      padding: 10px 16px calc(10px + max(0px, env(safe-area-inset-top)));
      background: color-mix(in srgb, var(--p-surface) 85%, transparent);
      backdrop-filter: blur(18px);
      -webkit-backdrop-filter: blur(18px);
      border-bottom: 1px solid color-mix(in srgb, var(--p-line) 50%, transparent);
      transition: opacity 0.4s ease, transform 0.4s ease;
    }

    .presentation-title {
      min-width: 0;
      overflow: hidden;
      white-space: nowrap;
      text-overflow: ellipsis;
      font-weight: 760;
      font-size: 1.1rem;
      color: var(--p-text);
    }

    .presentation-controls .button {
      background: var(--p-surface);
      color: var(--p-text);
      border-color: var(--p-line);
    }

    .presentation-stage {
      flex: 1;
      overflow: auto;
      scroll-behavior: smooth;
      padding: clamp(16px, 4vw, 56px);
      padding-top: calc(80px + env(safe-area-inset-top));
      padding-bottom: 50dvh;
    }

    .presentation-text {
      width: min(100%, var(--presentation-width, 920px));
      margin: 0 auto;
      font-family: var(--chart-font);
      font-size: var(--presentation-font);
      line-height: 1.5;
      white-space: pre-wrap;
      overflow-wrap: anywhere;
      color: var(--p-text);
    }

    .presentation.orientation-landscape {
      --presentation-width: 1180px;
    }

    .presentation.orientation-portrait {
      --presentation-width: 760px;
    }

    .presentation-controls-bottom {
      position: absolute;
      bottom: max(24px, env(safe-area-inset-bottom));
      left: 50%;
      transform: translateX(-50%);
      display: flex;
      align-items: center;
      gap: 10px;
      padding: 10px 16px;
      background: color-mix(in srgb, var(--p-surface) 85%, transparent);
      backdrop-filter: blur(16px);
      -webkit-backdrop-filter: blur(16px);
      border: 1px solid color-mix(in srgb, var(--p-line) 50%, transparent);
      border-radius: 999px;
      box-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
      transition: opacity 0.4s ease, transform 0.4s ease;
      z-index: 510;
    }

    .presentation-controls-bottom .icon-button {
      border: none;
      background: transparent;
      border-radius: 50%;
      width: 40px;
      height: 40px;
      color: var(--p-text);
    }

    .presentation.idle .presentation-top {
      opacity: 0;
      transform: translateY(-100%);
      pointer-events: none;
    }

    .presentation.idle .presentation-controls-bottom {
      opacity: 0;
      transform: translate(-50%, 20px);
      pointer-events: none;
    }

    .print-area {
      display: none;
    }

    @media print {
      body {
        background: #fff;
        color: #000;
      }

      body> :not(.print-area) {
        display: none !important;
      }

      .app-shell,
      .modal-host,
      .toast-host {
        display: none !important;
      }

      .print-area {
        display: block !important;
        padding: 20px;
      }

      .print-area h1 {
        font-family: sans-serif;
        font-size: 24px;
        margin: 0 0 10px;
        font-weight: bold;
      }

      .print-area pre {
        font-family: monospace;
        font-size: 12px;
        white-space: pre-wrap;
        line-height: 1.5;
        margin: 0;
      }

      .print-area footer {
        font-family: sans-serif;
        font-size: 10px;
        color: #666;
        margin-top: 20px;
        border-top: 1px solid #ccc;
        padding-top: 10px;
      }
    }

    .visually-hidden {
      position: absolute;
      width: 1px;
      height: 1px;
      padding: 0;
      margin: -1px;
      overflow: hidden;
      clip: rect(0, 0, 0, 0);
      border: 0;
      white-space: nowrap;
    }

    .md-divider {
      border: 0;
      border-top: 1px dashed var(--line);
      margin: 12px 0;
    }

    .md-header {
      font-size: 1.25em;
      font-weight: bold;
      color: var(--accent);
      margin: 16px 0 8px;
      display: block;
      font-family: var(--ui-font);
    }

    .presentation .md-header {
      color: var(--p-accent);
    }

    .md-subheader {
      font-size: 1.1em;
      font-weight: 600;
      color: var(--accent);
      margin: 12px 0 6px;
      display: block;
      font-family: var(--ui-font);
    }

    .presentation .md-subheader {
      color: var(--p-accent);
    }

    .md-note {
      color: var(--muted);
      font-style: italic;
      background: var(--surface-2);
      padding: 4px 8px;
      border-left: 3px solid var(--line);
      display: inline-block;
      margin: 4px 0;
      border-radius: 0 4px 4px 0;
      font-family: var(--ui-font);
      font-size: 0.9em;
    }

    .presentation .md-note {
      color: var(--p-muted);
      background: color-mix(in srgb, var(--p-surface) 90%, transparent);
      border-left: 3px solid var(--p-line);
    }

    .presentation .md-divider {
      border-color: var(--p-line);
    }

    .presentation-controls .select {
      background: var(--p-surface);
      color: var(--p-text);
      border-color: var(--p-line);
    }

    .presentation-controls .help-icon {
      background: var(--p-surface);
      color: var(--p-muted);
      border: 1px solid var(--p-line);
    }

    .presentation-controls-bottom input[type="range"] {
      accent-color: var(--p-accent);
    }

    .presentation .beat-dot {
      background: var(--p-line);
    }

    .presentation .beat-dot.active {
      background: var(--p-accent);
    }

    .md-chord-line,
    .md-chord,
    .chord-bold {
      color: var(--accent);
      font-weight: 800;
    }

    .md-slash {
      color: var(--warning-slash);
      font-weight: 800;
    }

    .presentation .md-chord-line,
    .presentation .md-chord,
    .presentation .chord-bold {
      color: var(--p-accent);
    }

    .presentation .md-slash {
      color: var(--p-slash);
    }

    /* ─── Responsive Breakpoints & Multi-Device Architecture ─── */

    /* ── 1. Extra Large Desktop (≥ 1440px) ── */
    @media (min-width: 1440px) {
      .workspace {
        max-width: 1560px;
        padding: 20px 32px;
        gap: 16px;
      }

      .tools-grid-layout {
        grid-template-columns: repeat(3, minmax(0, 1fr));
        gap: 20px;
      }

      .editor-split-container {
        grid-template-columns: minmax(380px, 1fr) minmax(460px, 1.35fr);
        gap: 20px;
        padding: 16px 20px;
      }

      .library-list {
        grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
      }

      .topbar {
        padding: 10px 28px;
        gap: 18px;
      }

      .brand-subtitle {
        display: block;
      }

      .top-nav-btn {
        padding: 0 15px;
        font-size: 0.86rem;
      }

      .top-actions {
        gap: 8px;
      }
    }

    /* ── 2. Desktop & Laptop Common (≥ 1024px) ── */
    @media (min-width: 1024px) {
      .top-nav {
        display: flex !important;
      }

      .top-actions {
        display: flex !important;
      }

      .topbar-menu-btn {
        display: inline-flex !important;
      }

      .topbar-mobile-actions {
        display: none !important;
      }

      .mobile-view-switcher {
        display: none !important;
      }

      .mobile-editor-mode-toggle {
        display: none !important;
      }

      .desktop-preview-mode-switch {
        display: inline-flex !important;
      }

      .editor-split-container {
        display: grid !important;
      }

      .editor-pane-left,
      .editor-pane-right {
        display: flex !important;
      }

      /* Secondary tools live in the accessible slide-out sidebar drawer */
      #helpButton,
      #settingsButton,
      #langSelect,
      #headerInstallBtn {
        display: none !important;
      }
    }

    /* ── 3a. Standard Laptop (1200px – 1439px) ── */
    @media (min-width: 1200px) and (max-width: 1439px) {
      .topbar {
        gap: 12px;
        padding: 8px 18px;
      }

      .brand {
        gap: 8px;
      }

      .brand-title {
        font-size: 1.08rem;
      }

      .brand-subtitle {
        display: none;
      }

      .top-nav {
        gap: 3px;
        padding: 3px;
      }

      .top-nav-btn {
        padding: 0 11px;
        font-size: 0.83rem;
        min-height: 33px;
      }

      .top-actions {
        gap: 8px;
      }

      #topbarUserGreeting {
        max-width: 85px;
        overflow: hidden;
        text-overflow: ellipsis;
        white-space: nowrap;
      }

      .tools-grid-layout {
        grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
        gap: 14px;
      }

      .editor-split-container {
        grid-template-columns: minmax(300px, 1fr) minmax(340px, 1.2fr);
        gap: 14px;
        padding: 10px 12px;
      }
    }

    /* ── 3b. Compact Laptop (1024px – 1199px) ── */
    @media (min-width: 1024px) and (max-width: 1199px) {
      .topbar {
        gap: 8px;
        padding: 8px 12px;
      }

      .brand {
        gap: 6px;
      }

      .brand-logo {
        width: 30px;
        height: 30px;
      }

      .brand-title {
        font-size: 1rem;
      }

      .brand-subtitle {
        display: none;
      }

      .top-nav {
        gap: 2px;
        padding: 2px;
      }

      .top-nav-btn {
        padding: 0 8px;
        font-size: 0.78rem;
        min-height: 30px;
        gap: 4px;
      }

      .top-actions {
        gap: 6px;
      }

      #googleSyncButton .button-label {
        display: none !important;
      }

      #googleSyncButton {
        padding: 0 8px;
        min-height: 32px;
        min-width: 32px;
        justify-content: center;
      }

      #topbarUserGreeting {
        display: none !important;
      }

      #topbarProfileContainer {
        padding: 2px;
        border: none;
        background: transparent;
      }

      .tools-grid-layout {
        grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
        gap: 12px;
      }

      .editor-split-container {
        grid-template-columns: minmax(280px, 1fr) minmax(300px, 1.15fr);
        gap: 12px;
        padding: 8px 10px;
      }
    }


    /* ── 4. Tablet Range (768px – 1023px) ── */
    @media (min-width: 768px) and (max-width: 1023px) {
      :root {
        --panel-pad: 14px;
      }

      .topbar {
        padding: 8px 16px;
        gap: 10px;
        min-height: calc(56px + env(safe-area-inset-top, 0px));
      }

      .topbar-menu-btn {
        display: inline-flex !important;
      }

      .brand {
        gap: 8px;
      }

      .brand-title {
        font-size: 1.05rem;
      }

      .top-nav {
        display: flex !important;
        padding: 2px;
        gap: 2px;
      }

      .top-nav-btn {
        padding: 0 8px;
        font-size: 0.78rem;
        min-height: 30px;
        gap: 4px;
      }

      .top-actions {
        display: none !important;
      }

      .topbar-mobile-actions {
        display: flex !important;
        margin-left: auto;
        gap: 8px;
        align-items: center;
      }

      .mobile-view-switcher {
        display: none !important;
      }

      .brand-subtitle {
        display: none;
      }

      .workspace {
        padding: 12px 16px 24px;
        gap: 12px;
      }

      .tools-grid-layout {
        grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 14px;
      }

      .library-list {
        grid-template-columns: repeat(2, minmax(0, 1fr));
      }

      .editor-split-container {
        display: grid !important;
        grid-template-columns: minmax(0, 1fr) minmax(0, 1.15fr);
        gap: 12px;
        padding: 10px;
      }

      .editor-pane-left,
      .editor-pane-right {
        display: flex !important;
      }

      .desktop-preview-mode-switch {
        display: inline-flex !important;
      }

      .mobile-editor-mode-toggle {
        display: none !important;
      }

      .piano-key-white {
        width: clamp(40px, 4.2vw, 54px);
      }

      .piano-key-black {
        width: clamp(26px, 2.6vw, 34px);
        margin-left: clamp(-13px, -1.3vw, -17px);
        margin-right: clamp(-13px, -1.3vw, -17px);
      }
    }

    /* ── 5. All Mobile Screens (≤ 767px) ── */
    @media (max-width: 767px) {
      :root {
        --panel-pad: 12px;
        --tap-size: 44px;
      }

      .top-nav {
        display: none !important;
      }

      .top-actions {
        display: none !important;
      }

      .topbar-menu-btn {
        display: inline-flex !important;
      }

      .topbar-mobile-actions {
        display: flex !important;
        margin-left: auto;
        gap: 7px;
        align-items: center;
      }

      .mobile-view-switcher {
        display: grid !important;
      }

      .topbar {
        align-items: center;
        min-height: calc(54px + env(safe-area-inset-top, 0px));
        padding-top: calc(8px + env(safe-area-inset-top, 0px));
        padding-bottom: 8px;
        padding-left: calc(10px + env(safe-area-inset-left, 0px));
        padding-right: calc(10px + env(safe-area-inset-right, 0px));
        gap: 8px;
      }

      .brand {
        gap: 8px;
      }

      .brand-logo {
        width: 30px;
        height: 30px;
        border-radius: 8px;
      }

      .brand-title {
        font-size: 1.02rem;
      }

      .version-badge {
        font-size: 0.65rem;
        padding: 1px 6px;
      }

      .brand-subtitle {
        display: none;
      }

      .workspace {
        padding: 8px 8px calc(80px + env(safe-area-inset-bottom, 0px));
        gap: 10px;
      }

      .editor-split-container {
        grid-template-columns: 1fr;
        padding: 6px;
        gap: 8px;
      }

      .mobile-editor-mode-toggle {
        display: inline-flex !important;
      }

      .desktop-preview-mode-switch {
        display: none !important;
      }

      /* Pane visibility based on data-mobile-pane */
      .editor-panel[data-mobile-pane="edit"] .editor-pane-left {
        display: flex !important;
      }
      .editor-panel[data-mobile-pane="edit"] .editor-pane-right {
        display: none !important;
      }

      .editor-panel[data-mobile-pane="preview"] .editor-pane-left {
        display: none !important;
      }
      .editor-panel[data-mobile-pane="preview"] .editor-pane-right {
        display: flex !important;
      }
      .editor-panel[data-mobile-pane="preview"] .desktop-preview-mode-switch {
        display: inline-flex !important;
      }

      .editor-panel[data-mobile-pane="split"] .editor-pane-left {
        display: flex !important;
      }
      .editor-panel[data-mobile-pane="split"] .editor-pane-right {
        display: flex !important;
      }
      .editor-panel[data-mobile-pane="split"] .desktop-preview-mode-switch {
        display: inline-flex !important;
      }

      .editor-placeholder {
        padding: 18px 14px;
        justify-content: flex-start;
        padding-top: 20px;
      }

      .editor-placeholder h3 {
        font-size: 1.1rem;
        margin-bottom: 6px;
      }

      .editor-placeholder p {
        font-size: 0.84rem;
        margin-bottom: 10px;
        line-height: 1.4;
      }

      .editor-placeholder ul {
        font-size: 0.8rem;
        line-height: 1.55;
      }

      .editor-placeholder li {
        margin-bottom: 4px;
        gap: 6px;
      }

      .editor-placeholder code {
        padding: 2px 5px;
        min-width: 40px;
      }

      .library-list {
        grid-template-columns: 1fr;
      }

      .tools-grid-layout {
        grid-template-columns: 1fr;
        gap: 12px;
      }

      .editor-toolbar {
        padding: 8px 10px;
        display: flex;
        flex-wrap: wrap;
        align-items: center;
        justify-content: space-between;
        gap: 8px;
        background: var(--surface-2);
        border-bottom: 1px solid var(--line);
      }

      .toolbar {
        display: flex;
        flex-wrap: wrap;
        gap: 6px;
        align-items: center;
      }

      .mobile-editor-mode-toggle .tab-button {
        padding: 4px 10px;
        font-size: 0.78rem;
        min-height: 32px;
      }

      .button {
        min-height: var(--tap-size);
        padding: 0 10px;
      }

      .toolbar .button {
        padding: 0 9px;
        min-height: 34px;
        font-size: 0.8rem;
        gap: 4px;
      }

      .toolbar .button .icon {
        width: 15px;
        height: 15px;
      }

      .song-title-input {
        min-height: 44px;
        padding: 8px 10px 4px;
        font-size: 1.05rem;
      }

      .textarea {
        min-height: calc(100dvh - 250px);
        padding: 12px;
        font-size: 0.88rem;
      }

      .metric-grid,
      .export-grid,
      .layout-row {
        grid-template-columns: 1fr;
      }

      .modal {
        max-height: calc(100dvh - 32px);
        width: calc(100vw - 20px);
        margin: 10px auto;
      }

      .toast-host {
        bottom: max(78px, calc(74px + env(safe-area-inset-bottom, 0px)));
      }

      .presentation-text {
        font-size: calc(var(--presentation-font) * 0.55) !important;
      }

      .presentation-stage {
        padding: 14px;
        padding-top: calc(84px + env(safe-area-inset-top, 0px));
        padding-bottom: 50dvh;
      }

      .presentation-top {
        padding: 8px 10px;
        flex-direction: column;
        gap: 6px;
      }

      .presentation-controls {
        display: flex;
        justify-content: space-between;
        gap: 4px;
        width: 100%;
      }

      .presentation-controls .button {
        font-size: 0.75rem;
        padding: 0 8px;
        min-height: 32px;
      }

      .presentation-controls-bottom {
        padding: 6px 10px;
        gap: 6px;
        bottom: calc(10px + env(safe-area-inset-bottom, 0px));
        flex-wrap: wrap;
        justify-content: center;
        max-width: 95vw;
      }

      .presentation-controls-bottom .icon-button {
        width: 36px;
        height: 36px;
      }

      .circle-container {
        max-width: min(85vw, 340px);
      }

      .piano-key-white {
        width: 38px;
        padding-bottom: 8px;
      }

      .piano-key-white .key-label {
        font-size: 0.75rem;
      }

      .piano-key-black {
        width: 24px;
        margin-left: -12px;
        margin-right: -12px;
        padding-bottom: 6px;
      }

      .piano-key-black .key-label {
        font-size: 0.65rem;
      }

      .fret-cell {
        min-width: 44px;
      }
    }

    /* ── 6. Extra Small Mobile (< 480px) ── */
    @media (max-width: 480px) {
      .topbar {
        padding-top: calc(6px + env(safe-area-inset-top, 0px));
        padding-bottom: 6px;
        padding-left: calc(8px + env(safe-area-inset-left, 0px));
        padding-right: calc(8px + env(safe-area-inset-right, 0px));
        gap: 6px;
      }

      .brand {
        gap: 6px;
      }

      .brand-logo {
        width: 28px;
        height: 28px;
        border-radius: 7px;
      }

      .brand-title {
        font-size: 0.96rem;
      }

      .version-badge {
        font-size: 0.65rem;
        padding: 1px 5px;
      }

      .topbar-menu-btn {
        width: 34px;
        height: 34px;
      }

      .topbar-mobile-actions {
        gap: 4px;
      }

      #mobileUserAvatar {
        width: 26px;
        height: 26px;
      }

      #themeToggleMobile {
        width: 34px;
        height: 34px;
      }

      .topbar-mobile-actions .button.compact {
        padding: 0 8px;
        font-size: 0.75rem;
        min-height: 32px;
      }

      .editor-toolbar {
        padding: 6px 8px;
        gap: 6px;
      }

      .toolbar {
        gap: 4px;
      }

      .toolbar .button {
        padding: 0 7px;
        font-size: 0.75rem;
        min-height: 30px;
      }

      .desktop-preview-mode-switch .tab-button,
      .mobile-editor-mode-toggle .tab-button {
        padding: 3px 8px;
        font-size: 0.72rem;
        min-height: 28px;
      }

      .circle-container {
        max-width: min(88vw, 300px);
      }

      .transpose-box {
        grid-template-columns: 32px minmax(0, 1fr) 32px !important;
        gap: 4px !important;
      }

      .beat-row {
        gap: 3px;
      }

      .beat-dot {
        width: 10px;
        height: 10px;
      }
    }

    /* ── 7. Ultra-Compact Mobile (< 360px) ── */
    @media (max-width: 360px) {
      .topbar {
        padding-left: calc(6px + env(safe-area-inset-left, 0px));
        padding-right: calc(6px + env(safe-area-inset-right, 0px));
        gap: 4px;
      }

      .mobile-view-switcher {
        padding: 4px 4px calc(4px + env(safe-area-inset-bottom, 0px)); min-height: calc(60px + env(safe-area-inset-bottom, 0px));
        gap: 2px;
      }

      .mobile-view-switcher .tab-button {
        min-height: 42px;
        padding: 2px;
        font-size: 0.68rem;
      }

      .mobile-view-switcher .tab-button .icon {
        width: 16px;
        height: 16px;
      }

      .brand-title {
        font-size: 0.88rem;
      }

      .brand-logo {
        width: 24px;
        height: 24px;
      }

      .version-badge {
        display: none;
      }

      .topbar-menu-btn {
        width: 32px;
        height: 32px;
      }

      #themeToggleMobile {
        width: 32px;
        height: 32px;
      }

      .topbar-mobile-actions .button.compact {
        padding: 0 6px;
        font-size: 0.72rem;
        min-height: 30px;
      }
    }



    /* ── 8. Landscape Mode on Mobile / Handhelds ── */
    @media (max-height: 520px) and (orientation: landscape) {
      .topbar {
        min-height: 42px;
        padding-top: 4px;
        padding-bottom: 4px;
      }

      .workspace {
        padding: 6px 12px calc(58px + env(safe-area-inset-bottom, 0px));
      }

      .mobile-view-switcher {
        height: 48px;
        padding: 3px 8px calc(3px + env(safe-area-inset-bottom, 0px));
      }

      .mobile-view-switcher .tab-button {
        min-height: 38px;
        font-size: 0.72rem;
      }

      .textarea {
        min-height: 140px;
      }

      .presentation-stage {
        padding-top: 56px;
      }
    }

    .manage-song-row:hover {
      background: color-mix(in srgb, var(--accent) 6%, var(--surface)) !important;
    }

    @keyframes qrScanLaser {
      0% { top: 0; opacity: 0.8; }
      50% { top: calc(100% - 2px); opacity: 1; }
      100% { top: 0; opacity: 0.8; }
    }

    /* AI Co-Writer Styles */
    .ai-fab {
      position: fixed;
      bottom: 24px;
      right: 24px;
      width: 56px;
      height: 56px;
      border-radius: 28px;
      background: linear-gradient(135deg, var(--accent), var(--accent-2));
      color: #fff;
      border: none;
      box-shadow: 0 4px 14px color-mix(in srgb, var(--accent) 40%, transparent);
      display: flex;
      align-items: center;
      justify-content: center;
      cursor: pointer;
      z-index: 900;
      transition: transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1), box-shadow 0.2s;
    }
    
    .ai-fab:hover {
      transform: scale(1.1);
      box-shadow: 0 6px 20px color-mix(in srgb, var(--accent) 60%, transparent);
    }

    @media (max-width: 480px) {
      .ai-fab {
        bottom: 80px;
        right: 16px;
      }
    }
    
    .ai-chat-panel {
      position: fixed;
      bottom: 90px;
      right: 24px;
      width: 360px;
      height: 500px;
      max-height: calc(100dvh - 120px);
      background: color-mix(in srgb, var(--surface) 95%, transparent);
      backdrop-filter: blur(20px);
      border: 1px solid var(--line);
      border-radius: 16px;
      box-shadow: var(--shadow);
      display: flex;
      flex-direction: column;
      z-index: 900;
      overflow: hidden;
      transition: opacity 0.3s, transform 0.3s;
      transform-origin: bottom right;
    }
    
    .ai-chat-panel.hidden {
      opacity: 0;
      pointer-events: none;
      transform: scale(0.9) translateY(20px);
    }
    
    .ai-chat-header {
      padding: 14px 16px;
      background: var(--surface-2);
      border-bottom: 1px solid var(--line);
      display: flex;
      justify-content: space-between;
      align-items: center;
    }
    
    .ai-chat-history {
      flex: 1;
      padding: 16px;
      overflow-y: auto;
      display: flex;
      flex-direction: column;
      gap: 12px;
      font-size: 0.9rem;
    }
    
    .ai-message {
      padding: 10px 14px;
      border-radius: 12px;
      max-width: 85%;
      line-height: 1.4;
      white-space: pre-wrap;
    }
    
    .ai-message.assistant {
      background: var(--surface-2);
      align-self: flex-start;
      border-bottom-left-radius: 4px;
    }
    
    .ai-message.user {
      background: var(--accent);
      color: #fff;
      align-self: flex-end;
      border-bottom-right-radius: 4px;
    }
    
    .ai-chat-input-area {
      padding: 12px;
      border-top: 1px solid var(--line);
      background: var(--surface);
      display: flex;
      gap: 8px;
    }
    
    .ai-chat-input-area textarea {
      flex: 1;
      resize: none;
      border: 1px solid var(--line);
      border-radius: 8px;
      padding: 8px 12px;
      font-size: 0.9rem;
      background: var(--surface-2);
      color: var(--text);
      outline: none;
      font-family: inherit;
    }
    
    .ai-chat-input-area textarea:focus {
      border-color: var(--accent);
    }
    
    @media (max-width: 600px) {
      .ai-chat-panel {
        width: calc(100% - 32px);
        right: 16px;
        bottom: calc(86px + env(safe-area-inset-bottom, 0px));
      }
      .ai-fab {
        right: 16px;
        bottom: calc(80px + env(safe-area-inset-bottom, 0px));
      }
    }

/* Accessibility focus-visible styles */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.button:focus-visible,
.icon-button:focus-visible,
.tab-button:focus-visible,
.top-nav-btn:focus-visible,
.sidebar-nav-btn:focus-visible,
.input:focus-visible,
.select:focus-visible,
.textarea:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}