/* --- 1. CSS 變數與主題定義 --- */
:root {
    /* 明亮模式 (保持原樣) */
    --color-text: #1f2937;
    --color-background: #f9fafb;
    --color-primary: #4f46e5;       
    --color-secondary: #e5e7eb;     
    --color-board-border: #9ca3af;
    --color-cell-empty: #ffffff;
    --color-cell-filled: #4b5563;   
    --color-piece-filled: #4f46e5;  
    --color-highlight: #facc15;     
    --color-preview: rgba(79, 70, 229, 0.5); 
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

*, *::before, *::after {
    box-sizing: border-box;
}

[data-theme='dark'] {
    /* 黑暗模式 (黑白灰美化) */
    --color-text: #ffffff;             
    --color-background: #111111;       
    --color-primary: #bbbbbb;          
    --color-secondary: #222222;        
    --color-board-border: #333333;     
    --color-cell-empty: #1a1a1a;       
    --color-cell-filled: #555555;      
    --color-piece-filled: #ffffff;     
    --color-highlight: #888888;        
    --color-preview: rgba(170, 170, 170, 0.4); 
    --shadow: 0 4px 15px rgba(0, 0, 0, 0.5);
}

/* --- 2. 全域設定 --- */
body {
    font-family: 'Segoe UI', system-ui, sans-serif;
    background-color: var(--color-background);
    color: var(--color-text);
    margin: 0;
    padding: 20px 20px 50px 20px; 
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    width: 100%;
    max-width: 900px;
    display: flex;
    flex-direction: column;
    gap: 30px;
    flex-grow: 1; 
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 0;
    border-bottom: 1px solid var(--color-board-border);
    margin-bottom: 30px;
}

h1 { 
    margin: 0; 
    font-size: 1.8rem; 
    color: var(--color-text); 
}
.instruction { margin-bottom: 10px; opacity: 0.8; }
.instruction-small { margin-top: 0; font-size: 0.9rem; opacity: 0.7; }
.section-title { margin: 0 0 10px 0; font-size: 1.2rem; }

/* --- 3. 按鈕 (略) --- */
button {
    cursor: pointer;
    padding: 10px 16px;
    border: none;
    border-radius: 8px;
    font-weight: 600;
    transition: opacity 0.2s, background-color 0.2s;
}
button:hover { opacity: 0.85; }

.btn-primary { 
    background-color: var(--color-primary); 
    color: var(--color-background); 
}
.btn-secondary { 
    background-color: var(--color-secondary); 
    color: var(--color-text); 
    border: 1px solid var(--color-board-border);
}
#theme-toggle { 
    background: var(--color-secondary); 
    border: 1px solid var(--color-board-border); 
    color: var(--color-text); 
}

.action-buttons {
    display: flex;
    gap: 10px;
    margin-top: 10px;
    margin-bottom: 10px;
    flex-wrap: wrap; 
    justify-content: center;
    width: 100%;
    max-width: 420px;
    margin-left: auto;
    margin-right: auto;
}

#continue-button:disabled, .btn-control:disabled {
    opacity: 0.4;
    cursor: not-allowed;
    color: var(--color-text);
}


/* --- 4. 核心輸入區 (棋盤與方塊並排/堆疊) --- */
#input-area-grid {
    display: flex;
    flex-direction: column; 
    align-items: center;
    gap: 30px;
    margin-bottom: 20px;
}

/* 寬螢幕媒體查詢 (並排佈局) */
@media (min-width: 768px) {
    #input-area-grid {
        flex-direction: row; 
        justify-content: center;
        align-items: center;
        gap: 40px;
    }
    
    #board-container {
        flex: 1 1 45%; 
        max-width: 420px;
    }
    
    #board-container .playback-controls {
        order: 3;
        margin-top: 10px;
    }

    #piece-input-area {
        flex: 1 1 45%;
        max-width: 420px;
        width: 100%;
        margin: 0;
    }
}

/* --- 5. 主棋盤 (8x8) --- */

/* 新增：修復手機上棋盤寬度過小的問題 */
#board-container {
    width: 100%;
    max-width: 420px;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

#board-container #board {
    order: 2;
}

#board-container .playback-controls {
    width: 100%;
    order: 1;
    margin: 0;
}

@media (min-width: 768px) {
    .action-buttons {
        align-self: flex-start;
        margin-left: 0;
        margin-right: 0;
    }
}

@media (max-width: 767px) {
    #board-container {
        width: 90%;
        margin: 0 auto;
    }
}

#board {
    display: grid;
    width: 100%; /* 確保棋盤佔滿其父容器 #board-container */
    border: 2px solid var(--color-board-border);
    background-color: var(--color-board-border);
    gap: 1px;
    box-shadow: var(--shadow);
}

#board {
    display: grid;
    width: 100%; /* 確保棋盤佔滿其父容器 #board-container */
    border: 2px solid var(--color-board-border);
    background-color: var(--color-board-border);
    gap: 1px;
    box-shadow: var(--shadow);
}

.cell {
    width: 100%;
    padding-bottom: 100%;
    background-color: var(--color-cell-empty);
    cursor: pointer;
    transition: background-color 0.1s;
    position: relative;
}

.cell.filled { background-color: var(--color-cell-filled); }

.cell.preview {
    background-color: var(--color-preview) !important;
    box-shadow: inset 0 0 0 2px var(--color-highlight); 
    z-index: 10;
}

/* --- 6. 待用方塊區 (5x5) --- */

/* 方塊區背景和邊界 */
#piece-input-area {
    padding: 20px;
    background-color: var(--color-secondary);
    border-radius: 12px;
    box-shadow: var(--shadow);
}

@media (max-width: 767px) {
    #piece-input-area {
        width: 90%;
        max-width: 420px;
        margin: 0 auto;
    }
}

.pieces-list {
    display: flex;
    flex-wrap: wrap;
    gap: 15px; 
    justify-content: center;
}

.piece-input-grid {
    display: grid;
    width: 158px;  
    height: 158px; 
    border: 2px solid var(--color-board-border);
    background-color: var(--color-cell-empty);
    gap: 1px;
    transition: border-color 0.2s;
}

.piece-input-grid.active-preview {
    border-color: var(--color-highlight);
    box-shadow: 0 0 10px var(--color-highlight);
}

.piece-input-cell {
    background-color: var(--color-cell-empty);
    cursor: pointer;
}

.piece-input-cell.filled {
    background-color: var(--color-piece-filled);
}

/* --- 7. 回放控制列 (略) --- */
.playback-controls {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 15px;
    margin: 15px 0;
    padding: 10px;
    background-color: var(--color-secondary);
    border-radius: 8px;
    transition: all 0.3s ease;
}

.playback-controls.hidden {
    display: none;
}

#step-indicator {
    font-weight: bold;
    font-family: monospace;
    font-size: 1.1rem;
    min-width: 120px;
    text-align: center;
}

.btn-control {
    background-color: transparent;
    border: 2px solid var(--color-primary);
    color: var(--color-primary);
    padding: 6px 16px;
}

.btn-control:hover:not(:disabled) {
    background-color: var(--color-primary);
    color: var(--color-background);
}

/* --- 8. Log 輸出區 (略) --- */
#output-log {
    margin-top: 10px;
    padding: 15px;
    background-color: var(--color-secondary);
    border-radius: 8px;
    font-family: monospace;
    font-size: 0.9rem;
    white-space: pre-wrap;
    line-height: 1.5;
    min-height: 100px;
    max-height: 300px;
    overflow-y: auto;
    border-left: 4px solid var(--color-primary);
    width: 100%;
    max-width: 900px;
}

/* --- 9. Footer (略) --- */
footer {
    width: 100%;
    max-width: 900px;
    margin: 30px auto 0;
    padding: 20px 0 0;
    border-top: 1px solid var(--color-board-border);
    text-align: center;
    color: var(--color-primary);
    font-size: 0.85rem;
    opacity: 0.6;
}