:root {
    /* --- LAYOUT & SIZING --- */
    --sidebar-l-width: 260px;
    --sidebar-r-width: 200px;
    --slot-height: 65px;
    --slot-gap: 12px;
    --piano-w: 160px;
    --piano-h: 350px;

    /* --- SPACING --- */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 10px;
    --space-lg: 15px;
    --space-xl: 20px;

    /* --- DAW COLOR PALETTE (v2.0) --- */
    --bg-color: #121214;
    --container-bg: #121214;   
    --panel-bg: #1e1e20;
    --panel-header: #252528;
    
    /* Theme Accents */
    --theme-r: 76; --theme-g: 175; --theme-b: 80;
    --theme-color: rgb(var(--theme-r), var(--theme-g), var(--theme-b));
    
    /* Borders & Separators */
    --border-color: #333336;
    --input-border: #444448;
    
    /* Inputs */
    --input-bg: #2a2a2c;
    --input-text: #eeeeee;
    --select-focus: var(--theme-color);
    
    /* Text */
    --text-main: #e0e0e0;
    --text-muted: #888888;
    
    /* Table / Grid */
    --table-bg: #121214;
    --th-bg: #2a2a2c;
    --th-text: #cccccc;
    --td-border: #222224;
    --td-bg: #18181a;
    --td-text: #bbbbbb;
    --td-hover-text: #000000;
    
    /* Highlights */
    --active-row-bg: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.15);
    --active-mode-bg: var(--theme-color);
    --active-mode-text: #ffffff;
    
    /* Secondary Chords */
    --sec-color: #ba68c8;
    --sec-row-bg: rgba(186, 104, 200, 0.1);
    --sec-text: #e1bee7;
    --sec-mode-bg: #8e24aa;
    
    /* Components */
    --slot-empty-bg: #151517;
    --slot-filled-bg: #202022;
    --slot-text: #e0e0e0;
    --slot-shadow: inset 0 2px 4px rgba(0,0,0,0.3);
    
    /* Buttons */
    --btn-base-bg: #2a2a2c;
    --btn-hover-bg: #3a3a3e;
    --btn-text: #e0e0e0;
    
    /* BPM Input */
    --bpm-bg: #000;
    --bpm-text: var(--theme-color);
    
    /* Visualizer */
    --viz-bg: #18181a;
    --viz-grid: #2a2a2c;
    --piano-white: #e0e0e0;
    --piano-black: #151515;
    --note-color: var(--theme-color);
    --strip-white: rgba(255, 255, 255, 0.04);
    
    /* Misc */
    --scrollbar-track: #121214;
    --scrollbar-thumb: #3a3a3e;
    --tooltip-bg: rgba(30, 30, 32, 0.95);
    --tooltip-border: #444;
    
    /* Mode Name BG */
    --mode-name-bg: #2a2a2c;
    --mode-name-text: #888;

    /* Custom Edit Mode Colors */
    --custom-note: #ffd700;
  }

  body.light-mode {
    --bg-color: #f2f3f5; 
    --container-bg: #f2f3f5;
    --panel-bg: #ffffff;
    --panel-header: #e2e8f0;
    --border-color: #e2e8f0;
    --input-border: #cbd5e0;
    
    --text-main: #2d3748;
    --text-muted: #718096;
    
    --input-bg: #fff;
    --input-text: #2d3748;
    
    --table-bg: #f2f3f5;
    --th-bg: var(--theme-color);
    --th-text: #fff;
    
    --td-bg: #fff;
    --td-text: #4a5568;
    --td-hover-text: #fff;
    
    --active-row-bg: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.1);
    --active-mode-text: #fff;

    /* [修改] 加深次屬和弦在白天的文字顏色，解決看不清楚的問題 */
    --sec-text: #7b1fa2; 
    --sec-row-bg: rgba(186, 104, 200, 0.15);

    --slot-empty-bg: #ffffff;
    --slot-filled-bg: #ffffff;
    --slot-text: #2d3748;
    --slot-shadow: inset 0 1px 3px rgba(0,0,0,0.1);
    
    --bpm-bg: #fff;
    --bpm-text: #2d3748;

    --viz-bg: #fff; --viz-grid: #e2e8f0;
    --piano-white: #fff;
    --piano-black: #555; 
    --strip-white: rgba(0, 0, 0, 0.03);

    --mode-name-bg: #e2e8f0;
    --mode-name-text: #4a5568;
    
    --btn-base-bg: #edf2f7;
    --btn-hover-bg: #e2e8f0;
    --btn-text: #4a5568;

    /* Light Mode Specifics */
    --scrollbar-track: #f2f3f5;
    --scrollbar-thumb: #cbd5e0;
    --tooltip-bg: rgba(255, 255, 255, 0.98);
  }

  * { box-sizing: border-box; }
  
  html, body { 
    margin: 0; padding: 0;
    width: 100vw; height: 100vh;
    overflow: hidden; 
    font-family: 'Inter', 'Noto Sans TC', system-ui, sans-serif; 
    background: var(--bg-color); color: var(--text-main); 
    font-size: 13px; user-select: none;
    transition: background 0.3s, color 0.3s;
  }

  /* SVG Icons */
  .icon { width: 100%; height: 100%; fill: currentColor; }
  .icon-sm { width: 14px; height: 14px; fill: currentColor; }

  /* Semantic Button Resets */
  button { font-family: inherit; }
  button.settings-trigger, button.theme-toggle-icon, button.lib-del, button.remove-x, button.sketchpad-toggle {
    background: none; border: none; padding: 0; margin: 0;
    cursor: pointer; color: inherit; font-size: inherit;
    display: flex; align-items: center; justify-content: center;
  }

  ::-webkit-scrollbar { width: 6px; height: 6px; }
  ::-webkit-scrollbar-track { background: var(--scrollbar-track); }
  ::-webkit-scrollbar-thumb { background-color: var(--scrollbar-thumb); border-radius: 3px; }
  ::-webkit-scrollbar-thumb:hover { background-color: var(--theme-color); }

  .main-wrapper { display: flex; flex-direction: row; height: 100%; width: 100%; overflow: hidden; }

  .sidebar-left { 
    width: var(--sidebar-l-width); height: 100%;
    background-color: var(--panel-bg); 
    border-right: 1px solid var(--border-color); 
    display: flex; flex-direction: column; flex-shrink: 0; 
    box-shadow: 2px 0 10px rgba(0,0,0,0.2); z-index: 10;
  }
  body.light-mode .sidebar-left { box-shadow: 2px 0 20px rgba(0,0,0,0.05); }
  .sidebar-scroll { flex: 1; overflow-y: auto; padding: var(--space-xl); display: flex; flex-direction: column; gap: 18px; }
  .sidebar-footer { 
    flex-shrink: 0; padding: 12px var(--space-xl); 
    border-top: 1px solid var(--border-color); 
    background-color: var(--panel-bg); 
    display: flex; align-items: center; justify-content: space-between; 
  }

  .content-center { 
    flex: 1; height: 100%; min-height: 0;
    background-color: var(--container-bg); 
    padding: var(--space-lg) var(--space-xl);
    overflow: hidden; 
    display: flex; flex-direction: column; gap: 1px;
    position: relative;
  }

  .sidebar-right { 
    width: var(--sidebar-r-width); height: 100%;
    background-color: var(--panel-bg); 
    border-left: 1px solid var(--border-color); 
    padding: var(--space-lg) var(--space-md); 
    display: flex; flex-direction: column; align-items: center; 
    overflow-y: auto; flex-shrink: 0; 
    box-shadow: -2px 0 10px rgba(0,0,0,0.2); z-index: 10;
  }
  body.light-mode .sidebar-right { box-shadow: -2px 0 20px rgba(0,0,0,0.05); }

  h2 { margin: 0; font-size: 1.2rem; text-align: center; color: var(--text-main); font-weight: 700; letter-spacing: -0.02em; }
  
  .control-group { display: flex; flex-direction: column; gap: var(--space-sm); }
  label { font-weight: 600; font-size: 0.85rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; }
  select { 
    padding: var(--space-md); font-size: 14px; border-radius: 4px; 
    border: 1px solid var(--input-border); background-color: var(--input-bg); 
    color: var(--input-text); cursor: pointer; outline: none; width: 100%; 
    font-family: inherit; transition: border-color 0.2s;
  }
  select:focus { border-color: var(--theme-color); }
  
  .checkbox-group { display: flex; align-items: center; gap: 12px; min-height: 28px; }
  .checkbox-group label { font-size: 0.9rem; color: var(--text-main); cursor: pointer; }
  input[type="checkbox"] { width: 18px; height: 18px; accent-color: var(--theme-color); cursor: pointer; background: var(--input-bg); border: 1px solid var(--input-border); border-radius: 3px; }
  .divider { border-bottom: 1px solid var(--border-color); margin: var(--space-sm) 0; opacity: 0.5; }

  .library-container { flex: 1; display: flex; flex-direction: column; gap: 12px; margin-top: var(--space-md); }
  .library-title { font-weight: 800; font-size: 1.1rem; color: var(--text-muted); display: flex; justify-content: space-between; align-items: center; text-transform: uppercase; letter-spacing: 0.05em; }
  .lib-card { 
    background-color: var(--btn-base-bg); border: 1px solid var(--border-color); border-radius: 6px; padding: var(--space-md); 
    cursor: grab; transition: all 0.2s ease; position: relative; 
  }
  .lib-card:hover { background-color: var(--btn-hover-bg); border-color: var(--theme-color); transform: translateY(-1px); }
  .lib-name { font-weight: 700; font-size: 14px; color: var(--text-main); margin-bottom: 2px; padding-right: var(--space-lg); }
  .lib-desc { font-size: 12px; color: var(--text-muted); }
  .lib-del { position: absolute; top: 8px; right: 8px; font-size: 14px; opacity: 0; transition: opacity 0.2s; color: var(--text-muted); }
  .lib-card:hover .lib-del { opacity: 0.5; }
  .lib-del:hover { opacity: 1; color: #ff5252; }

  .settings-panel { 
    position: absolute; bottom: 60px; left: var(--space-lg); width: 240px; 
    background: var(--tooltip-bg); backdrop-filter: blur(10px); color: var(--text-main);
    border: 1px solid var(--border-color); border-radius: 8px; 
    padding: 16px; z-index: 100; 
    box-shadow: 0 10px 40px rgba(0,0,0,0.5); display: none; 
    animation: fadeIn 0.2s ease-out;
  }
  .settings-panel.show { display: block; }
  .settings-mascot { width: 80px; display: block; margin: 0 auto 10px auto; filter: drop-shadow(0 2px 5px rgba(0,0,0,0.5)); }
  .setting-row { margin-bottom: var(--space-lg); }
  .color-dot { width: 20px; height: 20px; border-radius: 50%; cursor: pointer; border: 2px solid transparent; transition: transform 0.2s; }
  .color-dot:hover { transform: scale(1.2); }
  .color-dot.active { border-color: #fff; box-shadow: 0 0 8px rgba(255,255,255,0.3); }
  @keyframes fadeIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }

  .midi-hint { 
    display: flex; justify-content: space-between; align-items: center; 
    width: 100%; margin-bottom: 5px; padding: var(--space-sm) var(--space-lg); 
    background: var(--panel-bg); border: 1px solid var(--border-color); border-radius: 6px; font-size: 12px; flex-shrink: 0;
  }
  .midi-hint-text { color: var(--theme-color); font-weight: 600; display: flex; align-items: center; gap: var(--space-sm); }
  .help-container { position: relative; cursor: help; margin-left: var(--space-md); }
  .help-icon { width: 20px; height: 20px; background: rgba(255,255,255,0.1); border-radius: 50%; display: flex; align-items: center; justify-content: center; font-weight: bold; font-size: 12px; transition: 0.2s; }
  .help-icon:hover { background: var(--theme-color); color: #fff; }
  .tooltip-content { 
    visibility: hidden; width: 320px; background-color: var(--tooltip-bg); color: var(--text-main); 
    border: 1px solid var(--tooltip-border); border-radius: 6px; padding: var(--space-lg); 
    position: absolute; top: 30px; left: 50%; transform: translateX(-50%); 
    z-index: 200; box-shadow: 0 10px 30px rgba(0,0,0,0.8); opacity: 0; transition: opacity 0.2s; font-weight: normal; backdrop-filter: blur(5px);
  }
  .help-container:hover .tooltip-content { visibility: visible; opacity: 1; }

  .vol-control-wrapper { display: flex; align-items: center; gap: var(--space-sm); margin-left: auto; }
  #masterVol { width: 80px; height: 4px; accent-color: var(--theme-color); cursor: pointer; opacity: 0.7; transition: opacity 0.2s; }
  #masterVol:hover { opacity: 1; }
  .vol-icon { width: 16px; height: 16px; fill: currentColor; opacity: 0.7; }

  /* TABLE AREA - INDEPENDENT SCROLL */
  .table-container { 
    width: 100%; flex: 1; 
    overflow-y: auto; overflow-x: auto; 
    padding-bottom: 5px; background: var(--bg-color); border-radius: 6px; 
    min-height: 100px;
  }
  table { border-collapse: separate; border-spacing: var(--space-xs); width: 100%; table-layout: fixed; }
  th { padding: var(--space-md); background: var(--th-bg); color: var(--th-text); font-size: 11px; text-transform: uppercase; letter-spacing: 0.05em; border-radius: 4px; border: none; }
  td { 
    height: 50px; padding: 0; border: none; background-color: var(--td-bg); color: var(--td-text); 
    border-radius: 4px; position: relative; transition: all 0.1s; box-shadow: 0 1px 2px rgba(0,0,0,0.2);
  }
  body.light-mode td { box-shadow: 0 1px 2px rgba(0,0,0,0.05); }
  td:hover { background-color: var(--theme-color) !important; color: var(--td-hover-text) !important; transform: translateY(-2px); z-index: 5; box-shadow: 0 4px 12px rgba(0,0,0,0.4); }
  td.playing { background-color: var(--theme-color) !important; color: var(--td-hover-text) !important; box-shadow: 0 0 15px var(--theme-color) !important; transform: scale(0.98); }
  
  .active-row td { background-color: var(--active-row-bg); color: var(--theme-color); border: 1px solid rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.3); }
  .active-row .mode-name { background-color: var(--active-mode-bg) !important; color: var(--active-mode-text) !important; }
  .secondary-row td { background-color: var(--sec-row-bg); color: var(--sec-text); border: 1px solid rgba(186,104,200,0.3); }
  .secondary-row .mode-name { background-color: var(--sec-mode-bg) !important; color: #fff !important; }
  .mode-name { 
    font-weight: 700; font-size: 12px; padding-left: 12px; 
    background-color: var(--mode-name-bg); color: var(--mode-name-text); 
    border-radius: 4px; cursor: pointer; transition: 0.2s; 
  }
  .cell-inner { display: flex; width: 100%; height: 100%; align-items: center; justify-content: center; position: relative; }
  .cell-text { font-weight: 700; font-size: clamp(12px, 1.2vw, 16px); pointer-events: none; }
  .cell-inv-btns { position: absolute; right: 4px; top: 4px; bottom: 4px; display: none; flex-direction: column; justify-content: center; gap: 3px; }
  td:hover .cell-inv-btns { display: flex; }
  .cell-inv-btn { width: 14px; height: 14px; border: none; background: rgba(0,0,0,0.2); color: inherit; font-size: 8px; cursor: pointer; border-radius: 50%; display: flex; align-items: center; justify-content: center; }
  .cell-inv-btn:hover { background: rgba(0,0,0,0.5); color: #fff; }

  /* SKETCHPAD */
  .scratchpad-area { 
    background-color: var(--panel-bg); 
    padding: var(--space-lg) var(--space-xl); 
    border-radius: 8px; border: 1px solid var(--border-color); 
    margin-top: 0; flex-shrink: 0; z-index: 20; 
    box-shadow: 0 -4px 20px rgba(0,0,0,0.3); 
    transition: all 0.3s ease;
  }
  .scratchpad-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: var(--space-lg); }
  .icon-btn { 
    width: 32px; height: 32px; border-radius: 4px; 
    background: var(--btn-base-bg); color: var(--btn-text); 
    border: 1px solid var(--border-color); cursor: pointer; display: flex; align-items: center; justify-content: center; transition: all 0.2s; 
    padding: 0;
  }
  .icon-btn:hover { background: var(--btn-hover-bg); color: var(--theme-color); border-color: var(--theme-color); }
  .icon-btn.active { color: var(--theme-color); border-color: var(--theme-color); background: rgba(76,175,80,0.1); }
  #playBtn.playing { color: #ff5252; border-color: #ff5252; background: rgba(255,82,82,0.1); }
  
  .pad-controls { display: flex; align-items: center; gap: var(--space-lg); }
  .edit-group, .playback-group, .file-group { display: flex; align-items: center; gap: var(--space-sm); }
  
  /* FIXED BPM UI: SEPARATED BUTTON AND INPUT */
  .bpm-wrapper { display: flex; align-items: center; gap: var(--space-md); /* Space between input and button */ }
  .bpm-wrapper input { 
    width: 50px; background: var(--bpm-bg); border: 1px solid var(--border-color); 
    color: var(--bpm-text); font-family: 'Inter', monospace; font-weight: 700; text-align: center; 
    border-radius: 4px; padding: var(--space-xs); outline: none; -moz-appearance: textfield;
    appearance: none; /* 加上這行標準屬性 */ 
  }
  .bpm-wrapper input::-webkit-outer-spin-button, .bpm-wrapper input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
  .bpm-wrapper input:focus { border-color: var(--theme-color); box-shadow: 0 0 5px rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.3); }
  
  /* Independent Speed Button Style */
  .speed-btn {
    width: 32px; height: 30px; 
    border: 1px solid var(--border-color); border-radius: 4px;
    background: var(--btn-base-bg); color: var(--btn-text);
    font-size: 11px; font-weight: bold; cursor: pointer; transition: 0.2s;
    display: flex; align-items: center; justify-content: center;
  }
  .speed-btn:hover { background: var(--btn-hover-bg); border-color: var(--theme-color); }
  .speed-btn.x2 { color: var(--theme-color); border-color: var(--theme-color); background: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.1); }
  .speed-btn.x4 { color: #ff5252; border-color: #ff5252; background: rgba(255,82,82,0.1); }

  .file-group button { 
    padding: 6px 14px; border-radius: 4px; cursor: pointer; border: 1px solid var(--border-color); 
    font-weight: 600; font-size: 11px; text-transform: uppercase; letter-spacing: 0.05em; 
    background-color: var(--btn-base-bg); color: var(--btn-text);
    transition: all 0.2s ease; font-family: inherit; 
  }
  .file-group button:hover { background-color: var(--btn-hover-bg); border-color: var(--theme-color); color: #fff; }

  .sketchpad-toggle { margin-right: var(--space-md); font-size: 10px; opacity: 0.5; transition: transform 0.3s, opacity 0.3s; color: var(--text-main); width: 20px; height: 20px; }
  .sketchpad-toggle:hover { opacity: 1; }
  .sketchpad--collapsed .sketchpad-toggle { transform: rotate(-90deg); }
  .sketchpad--collapsed #slotsContainer, .sketchpad--collapsed .dice-btn, .sketchpad--collapsed .diceHint { display: none; }
  .sketchpad--collapsed { padding-top: var(--space-md); padding-bottom: var(--space-md); box-shadow: none; border-top: 1px solid var(--border-color); }
  .sketchpad--collapsed .scratchpad-header { margin-bottom: 0; }

  /* [修改] 1. Sketchpad 垂直擴充與捲軸 (修復骰子被遮擋問題) */
  .slots-container {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--slot-gap);
    width: 100%;
    /* 高度計算：(Slot 65px + Dice 24px + Gap 5px) * 2 rows + GridGap 12px ≈ 200px 
       設定 230px 確保兩排和弦 + 骰子都能完整顯示，不會被切掉
    */
    max-height: 200px; 
    overflow-y: auto; 
    transition: max-height 0.3s ease;
    padding-right: var(--space-xs);
    padding-bottom: 5px; /* 底部留一點空間 */
  }

  /* 展開狀態 */
  .slots-container.expanded {
    max-height: 620px; 
  }
  
  /* Expand Toggle Button */
  .expand-toggle-btn {
    background: transparent; border: none; color: var(--text-muted);
    cursor: pointer; font-size: 14px; padding: 4px;
    transition: 0.2s; display: flex; align-items: center; justify-content: center;
  }
  .expand-toggle-btn:hover { color: var(--theme-color); background: rgba(255,255,255,0.05); border-radius: 4px; }

  .slot { 
    width: 100%; height: var(--slot-height); 
    background-color: var(--slot-empty-bg); 
    border: 1px solid var(--border-color); border-radius: 6px; 
    display: flex; align-items: center; justify-content: space-between; 
    padding: 0 var(--space-sm); position: relative; transition: all 0.2s; 
    box-shadow: var(--slot-shadow);
  }
  .slot.drag-over { border-color: var(--theme-color); background: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.05); }
  .slot.filled { 
    border: 1px solid var(--border-color); 
    border-left: 4px solid var(--theme-color); 
    background-color: var(--slot-filled-bg); 
    color: var(--slot-text); 
    box-shadow: 0 4px 6px rgba(0,0,0,0.1); 
  }
  .slot.playing { background-color: var(--theme-color) !important; color: #fff !important; box-shadow: 0 0 20px var(--theme-color) !important; border-color: #fff; }
  .slot-text-wrapper { flex: 1; height: 100%; display: flex; align-items: center; justify-content: center; cursor: pointer; }
  .slot-text { font-size: 1.25rem; font-weight: 800; letter-spacing: -0.02em; }
  .slot-controls { display: flex; flex-direction: column; width: 24px; height: 100%; justify-content: center; align-items: center; margin-left: 5px; }
  .inv-btn { flex: 1; width: 100%; border: none; background: transparent; color: var(--text-muted); cursor: pointer; font-size: 9px; opacity: 0.5; transition: 0.2s; display: flex; align-items: center; justify-content: center; padding: 0; }
  .inv-btn:hover { color: var(--theme-color); opacity: 1; font-weight: bold; background: rgba(0,0,0,0.1); }
  
  /* [新增] 聲部連接磁鐵按鈕 */
  .smooth-btn {
    width: 100%; flex: 1; border: none; 
    background: transparent; color: var(--theme-color); 
    cursor: pointer; font-size: 10px; opacity: 0.7; 
    transition: 0.2s; display: flex; align-items: center; justify-content: center; 
    padding: 0; margin-bottom: 2px; border-bottom: 1px solid rgba(255,255,255,0.1);
  }
  .smooth-btn:hover { opacity: 1; background: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.15); transform: scale(1.1); }

  .dice-btn { 
    width: 100%; height: 24px; 
    background: var(--input-bg); border: 1px solid var(--border-color); 
    border-radius: 4px; cursor: pointer; color: var(--text-muted); 
    transition: all 0.2s; margin-top: var(--space-xs); 
    display: flex; align-items: center; justify-content: center; padding: 0;
  }
  .dice-btn svg { width: 14px; height: 14px; opacity: 0.6; fill: currentColor; transition: 0.2s; }
  .dice-btn:hover { background: var(--btn-hover-bg); border-color: #ffca28; color: #ffca28; }
  .dice-btn:hover svg { opacity: 1; fill: #ffca28; }
  
  /* [修改] 骰子禁用時不變紅，只降低透明度 */
  .dice-btn.disabled {
    cursor: not-allowed !important;
    opacity: 0.3;
  }

  /* [新增] 點擊時的錯誤閃爍動畫 */
  .dice-btn.error-flash {
    animation: flashRed 0.3s ease-in-out;
  }
  
  @keyframes flashRed {
    0% { background: var(--input-bg); color: var(--text-muted); }
    50% { background: #ff5252; border-color: #ff5252; color: #fff; }
    100% { background: var(--input-bg); color: var(--text-muted); }
  }

  .dice-btn.disabled svg {
    fill: white !important;
    opacity: 1 !important;
  }

  .remove-x { position: absolute; top: 2px; left: var(--space-xs); font-size: 12px; opacity: 0.2; cursor: pointer; z-index: 5; color: inherit; width: 16px; height: 16px; padding: 0; }
  .remove-x:hover { opacity: 1; color: var(--theme-color); }

  .piano-container-box { background: var(--panel-bg); border: 1px solid var(--border-color); border-radius: 8px; padding: var(--space-md); box-shadow: 0 4px 10px rgba(0,0,0,0.2); display: flex; flex-direction: column; align-items: center; gap: var(--space-md); margin-bottom: var(--space-lg); width: 100%; }
  
  /* PIANO TOOLBAR */
  .piano-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    height: 30px; 
    border-bottom: 1px solid var(--border-color);
    padding: 0 5px;
    background: var(--panel-header);
    border-radius: 8px 8px 0 0;
  }

  .pt-btn-group {
    display: flex;
    gap: var(--space-xs);
  }

  .pt-btn {
    width: 24px;
    height: 24px;
    border: 1px solid transparent;
    background: transparent;
    color: var(--text-muted);
    border-radius: 4px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
    padding: 0;
  }

  .pt-btn:hover {
    color: var(--theme-color);
    background: rgba(255,255,255,0.05);
  }

  .pt-btn.active {
    color: var(--bg-color); /* 文字反白 */
    background: var(--theme-color);
    border-color: var(--theme-color);
  }

  .pt-btn.eraser {
    color: #ff5252;
    display: none; /* 預設隱藏 */
  }
  .pt-btn.eraser:hover {
    background: rgba(255, 82, 82, 0.1);
  }

  .pt-drag-handle {
    cursor: grab;
  }
  .pt-drag-handle:active {
    cursor: grabbing;
  }
  
  #pianoCanvas { background: var(--viz-bg); border: 1px solid var(--border-color); border-radius: 4px; width: var(--piano-w); height: var(--piano-h); box-shadow: inset 0 0 10px rgba(0,0,0,0.3); cursor: pointer; }

  .bass-controls { display: flex; align-items: center; justify-content: space-between; width: 100%; margin-bottom: var(--space-md); padding: 0 5px; }
  .bass-ctrl-btn { background: var(--btn-base-bg); border: 1px solid var(--border-color); color: var(--btn-text); cursor: pointer; border-radius: 4px; width: 28px; height: 28px; font-size: 10px; transition: 0.2s; padding: 0; display: flex; align-items: center; justify-content: center; }
  .bass-ctrl-btn:hover { border-color: var(--theme-color); color: var(--theme-color); }
  #bassPalette { display: flex; flex-direction: column; gap: 3px; width: 100%; }
  .bass-key { width: 100%; height: 34px; background-color: #e0e0e0; color: #111; border: 1px solid #ccc; border-radius: 3px; display: flex; align-items: center; justify-content: center; font-weight: 800; cursor: grab; font-size: 12px; transition: all 0.1s; }
  body:not(.light-mode) .bass-key { background-color: #eeeeee; border-color: #333; }
  .bass-key.black-key { background-color: var(--piano-black) !important; color: #fff; border: 1px solid #000; }
  .bass-key:active { transform: scale(0.98); filter: brightness(0.9); }
  .bass-key:hover { border-color: var(--theme-color); z-index: 2; }

  #portal-tooltip { position: fixed; visibility: hidden; opacity: 0; width: 260px; background-color: var(--tooltip-bg); color: var(--text-main); border-radius: 6px; padding: 12px; z-index: 9999; box-shadow: 0 10px 30px rgba(0,0,0,0.8); border: 1px solid var(--theme-color); font-size: 12px; line-height: 1.5; pointer-events: none; transition: opacity 0.15s; backdrop-filter: blur(5px); }
  #portal-tooltip.show { visibility: visible; opacity: 1; }

  /* --- [CSS] 新增：捲動區域與重新命名按鈕 --- */
  #pianoScrollArea {
    width: var(--piano-w);
    height: var(--piano-h);
    overflow-y: hidden; 
    overflow-x: hidden; /* [修改] 強制隱藏 X 軸 */
    position: relative;
    background: var(--viz-bg);
    border-radius: 0 0 4px 4px; /* 下方圓角 */
  }
  /* 自訂捲軸樣式 (Chrome/Safari) */
  #pianoScrollArea::-webkit-scrollbar { width: 8px; }
  #pianoScrollArea::-webkit-scrollbar-track { background: var(--scrollbar-track); }
  #pianoScrollArea::-webkit-scrollbar-thumb { background-color: var(--scrollbar-thumb); border-radius: 4px; }
  #pianoScrollArea::-webkit-scrollbar-thumb:hover { background-color: var(--theme-color); }
  .rename-btn {
    flex: 1; width: 100%; border: none; background: transparent; 
    color: var(--text-muted); cursor: pointer; font-size: 12px; 
    opacity: 0.6; transition: 0.2s; display: flex; align-items: center; justify-content: center;
    padding: 0;
  }
  .rename-btn:hover { color: var(--theme-color); opacity: 1; font-weight: bold; }

  /* --- [Updated] 嵌入式轉調按鈕樣式 --- */
  .header-transpose-controls {
    display: flex; align-items: center; gap: 2px; margin-left: var(--space-sm);
    /* 稍微提高一點預設不透明度，讓新按鈕比較好找 */
    opacity: 0.5; transition: opacity 0.2s;
  }
  /* 滑鼠移過去時全亮 */
  .header-transpose-controls:hover { opacity: 1; }
  
  .h-sep {
    width: 1px; height: 14px; background-color: var(--text-main);
    opacity: 0.3; margin: 0 var(--space-xs);
  }
  
  .h-trans-btn {
    background: transparent; border: none; cursor: pointer;
    color: var(--text-main); padding: 0; width: 20px; height: 20px;
    display: flex; align-items: center; justify-content: center;
    border-radius: 4px; transition: all 0.2s;
    /* 確保裡面的 SVG 不會被擠壓 */
    flex-shrink: 0;
  }
  
  .h-trans-btn svg { width: 18px; height: 18px; fill: currentColor; }
  
  /* Hover 效果 */
  .h-trans-btn:hover { color: var(--theme-color); background: rgba(255,255,255,0.1); transform: translateY(-1px); }
  .h-trans-btn:active { transform: translateY(1px); }
  
  /* [新功能] 激活狀態的按鈕樣式 (用於五度圈模式) */
  .h-trans-btn.active {
    color: var(--theme-color);
    background: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.15);
    opacity: 1;
  }
  .settings-trigger { font-size: 18px; opacity: 0.6; }
  .theme-toggle-icon { font-size: 16px; opacity: 0.6; }

  /* --- [v2.3] UX & Modulation Advisor Styles --- */

/* 2. 右鍵選單 (Context Menu) */
.custom-context-menu {
  display: none; position: fixed; z-index: 2000;
  background: var(--panel-bg); border: 1px solid var(--border-color);
  box-shadow: 0 5px 20px rgba(0,0,0,0.6); border-radius: 6px;
  min-width: 180px; padding: 5px 0; font-family: 'Inter', sans-serif;
  backdrop-filter: blur(10px);
}
.ctx-item {
  padding: var(--space-sm) var(--space-lg); font-size: 12px; color: var(--text-main);
  cursor: pointer; display: flex; align-items: center; justify-content: space-between;
  transition: 0.1s; position: relative;
}
.ctx-item:hover { background: var(--theme-color); color: #fff; }
.ctx-shortcut { font-size: 10px; opacity: 0.5; }
.ctx-divider { height: 1px; background: var(--border-color); margin: 4px 0; opacity: 0.5; }
.ctx-arrow { font-size: 10px; opacity: 0.7; }

/* 子選單 (Submenu) */
.ctx-submenu {
  display: none; position: absolute; left: 100%; top: -5px;
  background: var(--panel-bg); border: 1px solid var(--border-color);
  border-radius: 6px; min-width: 120px; box-shadow: 0 5px 20px rgba(0,0,0,0.6);
}
.ctx-item:hover .ctx-submenu { display: block; }

/* 3. 轉調顧問面板 (Modulation Advisor) */
.mod-overlay {
  display: none; position: fixed; top: 0; left: 0; width: 100%; height: 100%;
  background: rgba(0,0,0,0.6); z-index: 3000; backdrop-filter: blur(3px);
  align-items: center; justify-content: center;
}
.mod-overlay.show { display: flex; animation: fadeIn 0.2s; }
.mod-panel {
  background: var(--panel-bg); width: 600px; max-width: 90%;
  border: 1px solid var(--border-color); border-radius: 12px;
  box-shadow: 0 20px 50px rgba(0,0,0,0.8);
  display: flex; flex-direction: column; overflow: hidden;
}
.mod-header {
  padding: var(--space-lg) var(--space-xl); background: var(--panel-header); border-bottom: 1px solid var(--border-color);
  display: flex; justify-content: space-between; align-items: center;
}
.mod-title { font-weight: 700; font-size: 16px; display: flex; align-items: center; gap: 8px; }
.mod-close { background: none; border: none; color: var(--text-muted); cursor: pointer; font-size: 18px; }
.mod-close:hover { color: #fff; }

.mod-body { padding: var(--space-xl); display: flex; flex-direction: column; gap: var(--space-xl); }
.mod-controls { display: flex; align-items: center; gap: var(--space-lg); justify-content: center; margin-bottom: var(--space-md); }
.mod-select { padding: var(--space-sm); background: var(--input-bg); border: 1px solid var(--border-color); color: var(--text-main); border-radius: 4px; font-weight: bold; }

.mod-grid { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-lg); }
.mod-card {
  background: var(--btn-base-bg); border: 1px solid var(--border-color);
  border-radius: 8px; padding: var(--space-lg); cursor: grab; position: relative;
  transition: 0.2s; display: flex; flex-direction: column; gap: var(--space-sm);
}
.mod-card:hover { border-color: var(--theme-color); background: var(--active-row-bg); transform: translateY(-2px); }
.mod-card:active { cursor: grabbing; }
.mod-card-title { font-weight: 700; font-size: 13px; color: var(--theme-color); }
.mod-card-desc { font-size: 11px; color: var(--text-muted); line-height: 1.4; }
.mod-card-prog { 
  margin-top: auto; padding: var(--space-sm); background: rgba(0,0,0,0.2); 
  border-radius: 4px; font-family: monospace; font-size: 12px; text-align: center; 
  display: flex; gap: 5px; justify-content: center;
}
.mod-chord-badge { background: var(--theme-color); color: #fff; padding: 2px 6px; border-radius: 3px; font-weight: bold; }

/* 4. Shift+Click 動畫 */
@keyframes pop-in { 0% { transform: scale(0.9); opacity: 0.5; } 50% { transform: scale(1.1); } 100% { transform: scale(1); opacity: 1; } }
.slot.just-filled { animation: pop-in 0.2s ease-out; border-color: var(--theme-color); }

    /* --- HARMONY NAVIGATOR STYLES (v2.0) --- */
    
    /* 1. 工具列上的小按鈕 */
    .hint-nav-btn {
        display: inline-flex; align-items: center; gap: 6px;
        background: rgba(255,255,255,0.1); 
        border: 1px solid rgba(255,255,255,0.2);
        color: var(--text-main);
        padding: 4px 10px; border-radius: 4px;
        margin-left: 15px; cursor: pointer;
        font-size: 11px; font-weight: 600;
        transition: all 0.2s; vertical-align: middle;
    }
    .hint-nav-btn:hover { background: rgba(255,255,255,0.2); border-color: var(--theme-color); }
    .hint-nav-btn.active {
        background: var(--theme-color); color: #fff; border-color: var(--theme-color);
        box-shadow: 0 0 10px rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.4);
    }

    /* 2. 視窗容器 (全螢幕遮罩置中) */
    .nav-modal-wrapper {
        position: fixed; top: 0; left: 0; width: 100vw; height: 100vh;
        z-index: 2000; pointer-events: none; /* 讓點擊穿透背景 */
        display: flex; align-items: center; justify-content: center;
    }

    /* 3. 視窗本體 */
    .nav-modal {
        width: 450px; height: 600px;
        background: #1a1a1d; 
        border: 1px solid var(--border-color);
        border-radius: 12px;
        box-shadow: 0 20px 60px rgba(0,0,0,0.8);
        display: flex; flex-direction: column;
        overflow: hidden; pointer-events: auto; /* 視窗本體可點擊 */
        animation: navPopIn 0.2s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    }
    @keyframes navPopIn { from { transform: scale(0.9); opacity: 0; } to { transform: scale(1); opacity: 1; }}

    /* Header */
    .nav-header {
        height: 50px; display: flex; align-items: center; justify-content: space-between;
        padding: 0 15px; border-bottom: 1px solid var(--border-color);
        background: var(--panel-header);
    }
    .nav-title-box { display: flex; flex-direction: column; align-items: center; }
    .nav-label { font-size: 10px; color: var(--text-muted); letter-spacing: 1px; font-weight: 700; }
    .nav-anchor-text { font-size: 15px; color: var(--theme-color); font-weight: 700; }
    .nav-icon-btn { background: none; border: none; color: var(--text-muted); cursor: pointer; padding: 6px; border-radius: 4px; display: flex; }
    .nav-icon-btn:hover { background: rgba(255,255,255,0.1); color: #fff; }

    /* Views */
    .nav-body { 
        /* 1. 佔滿剩餘空間 */
        flex: 1; 

        /* 2. 關鍵修改：允許垂直捲動 (原本是 hidden) */
        overflow-y: auto; 
        overflow-x: hidden;

        /* 3. 排版設定 */
        display: flex; 
        flex-direction: column; 
        position: relative; /* 確保子元素的定位基準 */
    }

    /* --- 請確保加上 Footer 的設定 --- */
    .nav-footer {
        /* 確保 Footer 固定在底部，不會跟著捲動，也不會被擠壓 */
        flex-shrink: 0;

        /* 你的 Footer 樣式，例如： */
        border-top: 1px solid var(--border-color);
        background: var(--panel-header); /* 或其他背景色 */
        padding: 10px; /* 根據你的設計調整 */
    }
    .nav-view-center { padding: 30px; gap: 20px; justify-content: center; }
    
    .dir-card {
        display: flex; align-items: center; gap: 20px;
        padding: 25px;
        background: var(--panel-bg);
        border: 1px solid var(--border-color);
        border-radius: 12px;
        color: var(--text-main);
        cursor: pointer; text-align: left;
        transition: all 0.2s;
    }
    .dir-card:hover { background: var(--container-bg); border-color: var(--theme-color); transform: translateY(-2px); box-shadow: 0 5px 15px rgba(0,0,0,0.2); }
    .dir-icon { color: var(--theme-color); opacity: 0.9; }
    .dir-title { font-size: 16px; font-weight: 700; margin-bottom: 4px; }
    .dir-desc { font-size: 13px; color: var(--text-muted); line-height: 1.4; }

    /* List View */
    .nav-list-container { background: var(--bg-color); }
    .nav-scroll-content { overflow-y: auto; padding: 15px; padding-bottom: 100px; }
    
    .nav-category { margin-bottom: 25px; }
    .cat-header { 
        font-size: 11px; font-weight: 800; color: var(--text-muted); 
        text-transform: uppercase; letter-spacing: 1px; margin-bottom: 10px;
        padding-bottom: 5px; border-bottom: 1px solid rgba(255,255,255,0.1);
    }
    .chord-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(85px, 1fr)); gap: 8px; }
    
    /* Chord Button */
    .nav-chord-wrapper {
        display: flex; border: 1px solid var(--border-color); border-radius: 6px;
        background: var(--panel-bg); overflow: hidden; transition: all 0.1s;
    }
    .nav-chord-wrapper:hover { border-color: var(--theme-color); transform: translateY(-1px); }
    
    .nav-chord-main {
        flex: 1; padding: 6px 4px; text-align: center; cursor: pointer;
        display: flex; flex-direction: column; justify-content: center;
    }
    .nav-chord-main:hover { background: rgba(255,255,255,0.05); }
    
    /* Add Button (+) */
    .nav-chord-add {
        width: 24px; background: rgba(0,0,0,0.2); border-left: 1px solid var(--border-color);
        color: var(--text-muted); cursor: pointer;
        display: flex; align-items: center; justify-content: center; font-size: 14px;
        transition: all 0.2s;
    }
    .nav-chord-add:hover { background: var(--theme-color); color: #fff; }

    .nc-name { font-size: 13px; font-weight: 600; display: block; }
    .nc-tag { font-size: 9px; opacity: 0.7; margin-top: 2px; display: block; zoom: 0.9; }

    /* Footer */
    .nav-footer {
        height: 110px; background: var(--panel-header);
        border-top: 1px solid var(--border-color);
        padding: 15px; display: flex; align-items: center;
        box-shadow: 0 -5px 15px rgba(0,0,0,0.2); z-index: 10;
    }
    .info-title { font-size: 15px; font-weight: 700; color: var(--theme-color); margin-bottom: 6px; }
    .info-desc { font-size: 12px; color: var(--text-muted); line-height: 1.5; }

    @media (max-width: 768px) {
        .nav-modal-wrapper { display: none !important; } /* 手機版隱藏 */
        .hint-nav-btn { display: none !important; }
    }

  /* --- RWD MOBILE STYLES --- */
  
  /* 預設隱藏手機版元件 */
  #mobileHeader, #mobileOverlay { display: none; }

  /* --- RWD 手機版專用樣式 (Clean Version) --- */
  @media (max-width: 768px) {
    .nav-wrapper { display: none !important; }

    :root {
      /* 設定變數：手機版左右側欄歸零 */
      --sidebar-l-width: 0px;
      --sidebar-r-width: 0px; 
      /* 鋼琴設為 0，因為我們不顯示了 */
      --piano-w: 0px; 
    }

    /* 1. Header 設定 (只保留左邊選單鈕，右邊鋼琴鈕隱藏) */
    #mobileHeader {
      display: flex;
      justify-content: space-between;
      align-items: center;
      height: 50px;
      padding: 0 15px;
      background-color: var(--panel-header);
      border-bottom: 1px solid var(--border-color);
      color: var(--text-main);
      position: relative;
      z-index: 1010;
    }
    .mobile-title { font-weight: 800; font-size: 14px; letter-spacing: 0.05em; }
    #mobileHeader button { background: none; border: none; color: inherit; cursor: pointer; padding: 5px; }
    
    /* 隱藏 Header 上的鋼琴按鈕，因為右側欄被拿掉了 */
    #mobilePianoBtn { display: none !important; }

    /* 2. 佈局調整 */
    .main-wrapper { 
        height: calc(100vh - 50px); 
        position: relative; 
    }
    
    /* 3. 左側欄 (設定選單) - 保留滑出功能 */
    .sidebar-left {
      position: absolute; top: 0; left: 0; height: 100%; width: 280px;
      background-color: var(--panel-bg); z-index: 1005;
      transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
      box-shadow: 0 0 20px rgba(0,0,0,0.5);
      transform: translateX(-100%); border-right: 1px solid var(--border-color);
    }
    .sidebar-left.show-mobile { transform: translateX(0); width: 80vw; max-width: 300px; }

    /* 4. 遮罩層 */
    #mobileOverlay {
      position: fixed; top: 0; left: 0; width: 100vw; height: 100vh;
      background: rgba(0,0,0,0.6); z-index: 1000;
      backdrop-filter: blur(2px); display: none; opacity: 0; transition: opacity 0.3s;
    }
    #mobileOverlay.active { display: block; opacity: 1; }


    /* --- [功能移除區] 徹底隱藏不需要的模組 --- */
    
    /* 移除 Chord Sketchpad 整塊區域 */
    .scratchpad-area { display: none !important; }
    
    /* 移除 右側欄 (MIDI Preview & Bass) */
    .sidebar-right { display: none !important; }

    /* 移除 上方提示文字 (Hint) */
    .midi-hint { display: none !important; }
    
    /* 移除 表格內的轉位箭頭 */
    .cell-inv-btns { display: none !important; }


    /* --- [表格優化區] 調式縮寫與凍結 --- */
    
    .table-container {
        /* 讓表格佔滿高度 (因為 Sketchpad 沒了) */
        height: 100% !important; 
        padding-bottom: 20px;
        overflow-x: auto; /* 允許左右滑動 */
    }

    /* 強制將原本的調式名稱隱藏，改用 data-abbr 顯示 */
    .mode-name { 
        font-size: 0 !important; 
        padding: 0 4px !important; 
        width: 40px !important; /* 縮小寬度 */
        text-align: center;
        
        /* 凍結首欄效果 */
        position: sticky; 
        left: 0;
        z-index: 20; 
        background-color: var(--panel-bg) !important;
        box-shadow: 2px 0 5px rgba(0,0,0,0.2);
    }
    
    /* 使用偽元素顯示縮寫 */
    .mode-name::after {
        content: attr(data-abbr); /* 抓取 JS 寫入的縮寫 */
        font-size: 11px;
        font-weight: 800;
        display: block;
        line-height: 50px; /* 垂直置中 */
        color: var(--text-muted);
    }

    /* --- [優化] 手機版細節調整 (V0.2) --- */

    /* 1. 隱藏側邊欄的「和弦庫」 */
    .library-container { display: none !important; }

    /* 2. 隱藏設定裡的「隨機包含次屬和弦」 */
    /* 透過選取 ID 來精準隱藏該選項與標籤 */
    #randomSec, label[for="randomSec"] { display: none !important; }

    /* 3. 和弦代號防爆框處理 */
    .cell-text {
        font-size: 10px !important;       /* 強制縮小字體 */
        letter-spacing: -0.5px !important; /* 縮緊字距，讓長和弦塞得進去 */
        white-space: nowrap !important;    /* 禁止換行 */
        transform: scale(0.95);           /* 稍微再縮小一點點以防萬一 */
    }
    td {
        padding: 0 1px !important; /* 減少格子的內距，爭取空間 */
    }

    /* 4. 表頭「調式名稱」改為「調式」並縮小 */
    /* 選取表格的第一個標題格 (也就是左上角那格) */
    th:first-child {
        font-size: 0 !important; /* 隱藏原本的「調式名稱」四個字 */
        width: 40px !important;  /* 強制寬度跟下方的縮寫欄位對齊 */
        padding: 0 !important;
        vertical-align: middle;
    }
    
    /* 使用偽元素填入新文字 */
    th:first-child::after {
        content: "調式"; 
        font-size: 11px;
        font-weight: bold;
        display: block;
        color: var(--th-text);
    }
  }
  /* --- [New] 點擊後保留的選取狀態 (Active State) --- */
/* 這是給和弦表 (Table) 用的 */
td.active {
  /* 使用內陰影模擬邊框 (Inset Shadow)，避免撐開表格導致跳動 */
  box-shadow: inset 0 0 0 2px var(--theme-color), 0 0 15px rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.4) !important;
  
  /* 微微的背景色，讓它與周圍區分 */
  background-color: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.15) !important;
  
  /* 確保文字顏色變亮，並加粗 */
  font-weight: 800 !important;
  z-index: 4; /* 層級比普通格子高，但比 Hover (5) 低 */
}

/* 確保文字顏色也跟著主題色變亮 */
td.active .cell-text {
  color: var(--theme-color) !important;
  opacity: 1;
}

/* 針對深色/淺色模式的微調 (可選) */
body.light-mode td.active {
  background-color: rgba(var(--theme-r), var(--theme-g), var(--theme-b), 0.1) !important;
  box-shadow: inset 0 0 0 2px var(--theme-color) !important;
}