:root {
    --primary-blue: #344860;
    --accent-blue: #4b6cb7;
    --bg-light: #f3f6fa;
    --cell-border-light: #bec6d4;
    --cell-border-dark: #344860;
    --cell-bg-selected: #b3d4ff;
    --cell-bg-highlight: #e2ecf8;
    --cell-bg-same-num: #c3d9ff;
    --text-given: #2e3a4e;
    --text-user: #033cb0;
    --text-error: #dc2626;
    --bg-error: #fee2e2;
    --text-notes: #6c757d;
    --note-yellow-bg: #fef08a;
    --note-yellow-text: #854d0e;
}

* { box-sizing: border-box; touch-action: manipulation; }

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Arial, sans-serif;
    background-color: #f8fafc;
    margin: 0;
    padding: 16px;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

/* 恢复最初舒适的容器大小，绝不撑大 */
.sudoku-container {
    display: flex;
    gap: 24px;
    max-width: 920px;
    width: 100%;
    background: #fff;
    padding: 20px;
    border-radius: 16px;
    box-shadow: 0 4px 24px rgba(0,0,0,0.08);
    align-items: flex-start;
}

.left-panel { 
    flex: 1; 
    display: flex; 
    flex-direction: column; 
    width: 100%;
    max-width: 520px;
    position: relative;
}

.header-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 14px;
    color: #666;
    margin-bottom: 10px;
    gap: 4px;
}

.mode-switch-group {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}
.mode-btn {
    padding: 5px 8px;
    font-size: 12px;
    font-weight: bold;
    border: 1px solid #cbd5e1;
    background-color: #f8fafc;
    color: #475569;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s;
}
.mode-btn:hover { background-color: #e2e8f0; }
.mode-btn.active {
    background-color: #4b6cb7;
    color: white;
    border-color: #4b6cb7;
}

.board-wrapper {
    position: relative;
    width: 100%;
    aspect-ratio: 1 / 1;
}

#sudoku-board {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    grid-template-rows: repeat(9, 1fr);
    width: 100%;
    height: 100%;
    border: 2px solid var(--cell-border-dark);
    user-select: none;
    background: #fff;
    box-sizing: border-box;
}

#line-svg {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    pointer-events: none;
    z-index: 10;
}
#line-svg.active { pointer-events: auto; cursor: crosshair; }

.cell {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: clamp(18px, 3.5vw, 28px);
    font-weight: 600;
    border: 1px solid var(--cell-border-light);
    cursor: pointer;
    background-color: #fff;
    position: relative;
    box-sizing: border-box;
    transition: background-color 0.1s, color 0.1s;
}

.cell:nth-child(3n) { border-right: 2px solid var(--cell-border-dark); }
.cell:nth-child(9n) { border-right: 1px solid var(--cell-border-light); }
.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid var(--cell-border-dark); }

.cell.diagonal-cell { background-color: rgba(75, 108, 183, 0.03); }
.cell.given { color: var(--text-given); font-weight: bold; }
.cell.user-entered { color: var(--text-user); }
.cell.invalid { color: var(--text-error) !important; background-color: var(--bg-error) !important; font-weight: bold; }
.cell.selected { background-color: var(--cell-bg-selected) !important; }
.cell.highlighted { background-color: var(--cell-bg-highlight); }
.cell.same-num { background-color: #c3d9ff !important; }

.notes-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    width: 100%; height: 100%;
    pointer-events: none;
}
.note-num {
    font-size: clamp(9px, 1.6vw, 13px);
    color: var(--text-notes);
    display: flex; align-items: center; justify-content: center;
    border-radius: 50%;
    pointer-events: auto;
}
.note-num.highlighted-note { background-color: #8adb8e !important; color: #fff !important; font-weight: bold; }
.note-num.yellow-marked { background-color: var(--note-yellow-bg) !important; color: var(--note-yellow-text) !important; font-weight: bold; }
.note-num.chain-purple { background-color: #c084fc !important; color: #fff !important; font-weight: bold; }
.note-num.chain-green { background-color: #4ade80 !important; color: #fff !important; font-weight: bold; }

/* 右侧面板整体布局调整 */
.right-panel {
    width: 320px !important;
    min-width: 320px !important;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-self: stretch;
    padding-top: 48px !important; 
    gap: 15px;
}

/* 统计栏（时间、错误、得分）样式微调 */
.stats-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
    font-size: 13px;
    color: #555;
    background: #f8fafc;
    padding: 8px 12px;
    border-radius: 8px;
}
.stats-bar .score { font-size: 15px; font-weight: bold; color: #333; }

.tools-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 25px;
}

/* 工具按钮通用样式 */
.tool-btn {
    width: 46px !important;
    height: 46px !important;
    border-radius: 8px !important;
    border: 1px solid #dcdcdc !important;
    cursor: pointer;
    display: flex !important;
    justify-content: center;
    align-items: center;
    font-size: 24px !important;
    margin-right: 10px !important;
    background-color: #ffffff;
    transition: all 0.2s ease-in-out !important;
}

.tool-btn:hover {
    transform: translateY(-2px) !important;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15) !important;
    border-color: #c0c0c0 !important;
    background-color: #e2e8f0;
}

.tool-btn:active {
    transform: translateY(0) !important;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1) !important;
    background-color: #f5f5f5 !important;
}

.tool-btn:last-child {
    margin-right: 0 !important;
}

.tool-btn svg { width: 16px; height: 16px; fill: currentColor; }

/* 工具按钮被选中（激活）时的样式 */
.tool-btn.active {
    background-color: #d8b4fe !important;
    color: #581c87 !important;
    border-color: #a855f7 !important;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.1);
}

.badge {
    position: absolute; top: -4px; right: -4px;
    background: #1976d2; color: white;
    font-size: 8px; font-weight: bold; padding: 1px 4px; border-radius: 8px;
}

.yellow-btn { background-color: #fef9c3 !important; color: #a16207 !important; border: 1px solid #fef08a !important; }
.yellow-btn.active { background-color: #eab308 !important; color: #fff !important; }

.red-line-btn { background-color: #fee2e2 !important; color: #dc2626 !important; border: 1px solid #fca5a5 !important; }
.red-line-btn.active { background-color: #ef4444 !important; color: #fff !important; }

/* 3 列数字键盘样式 */
.numpad {
    display: block !important;
    width: 100% !important;
    padding-left: 12px !important;
    margin-top: 15px !important;
    margin-bottom: 12px !important;
    overflow: hidden !important;
    box-sizing: border-box !important;
}

/* 数字按钮默认样式（平时带有好看的底色） */
.num-btn {
    float: left !important;
    width: 31% !important;
    margin-right: 3% !important;
    margin-bottom: 8px !important;
    height: 66px !important; 
    font-size: 22px !important; 
    font-weight: bold;
    border-radius: 8px;
    border: 1px solid #cbd5e1 !important;
    background: #f8fafc !important;  /* 按钮默认背景色 */
    color: #1e293b !important;
    cursor: pointer;
    display: flex !important;
    justify-content: center;
    align-items: center;
    box-sizing: border-box !important;
    box-shadow: 0 1px 2px rgba(0,0,0,0.05);
    transition: all 0.2s ease !important;
    position: relative; /* 必须有 */
}

/* 数字按钮悬停与点击效果 */
.num-btn:hover { 
    background-color: #e2ebf8 !important; 
    border-color: #94a3b8 !important;
}
.num-btn:hover::after {
    color: #e2ebf8 !important; /* 让悬停时的√颜色 = 悬停背景色，彻底隐形 */
}
.num-btn:active { 
    background-color: #cbd5e1 !important; 
}
.num-btn:active::after {
    color: #cbd5e1 !important; 
}
/* 默认状态下的勾：颜色和初始背景或默认文字融为一体（隐形） */
.num-btn::after {
    content: "✓";
    position: absolute;
    top: 8px;
    right: 10px;
    font-size: 13px;
    font-weight: bold;
    color: #f8fafc !important; /* 平时隐形 */
    line-height: 1;
    pointer-events: none;
    transition: color 0.2s ease !important; /* 让颜色变化更顺滑 */
}

/* 填满 9 个后的状态：变成禁用/完成颜色 */
.num-btn.completed {
    opacity: 0.5 !important;           /* 降低透明度（半透明效果），让它看起来变淡、处于非活跃状态 */
    background-color: #bbcce2 !important;/* 将背景颜色变成浅灰色，视觉上与未完成的按钮区分开 */
    color: #94a3b8 !important;         /* 将文字颜色变成浅灰色，使其不那么显眼 */
    border-color: #cbd5e1 !important;  /* 将边框颜色也改成浅灰色，保持整体边框协调 */
    cursor: not-allowed !important;    /* 鼠标悬停时显示“禁止通行”的小图标指针，提示用户该数字已完成 */
    box-shadow: none !important;       /* 移除按钮原本的阴影效果，让它看起来是平整凹陷的 */
}
/* 保证每行第 3 个按钮右边距为 0，防止错位 */
.num-btn:nth-child(3n) {
    margin-right: 0 !important;
}


/* “新游戏”按钮推到底部 */
.new-game-btn {
    width: 100%;
    padding: 12px;
    font-size: 15px;
    font-weight: bold;
    color: white;
    background-color: #4c73bf;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    margin-top: auto;
}
.new-game-btn:hover { background-color: #3b5f9e; }

.modal-overlay {
    position: fixed; top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0,0,0,0.5); display: none;
    justify-content: center; align-items: center; z-index: 1000;
}
.modal-box {
    background: white; padding: 24px; border-radius: 12px;
    width: 300px; text-align: center; box-shadow: 0 4px 20px rgba(0,0,0,0.15);
}
.modal-buttons {
    display: flex; gap: 12px; margin-top: 20px; justify-content: center;
}
.modal-btn {
    padding: 8px 16px; border-radius: 6px; border: none; font-weight: bold; cursor: pointer;
}
.modal-btn.confirm { background: #dc2626; color: white; }
.modal-btn.cancel { background: #e2e8f0; color: #475569; }

.session-log-view {
    margin-top: 6px; background: #1e293b; color: #38bdf8; padding: 6px 8px;
    border-radius: 6px; font-size: 10px; max-height: 80px; overflow-y: auto; text-align: left;
}

/* ==================== 手机端专属响应式布局调整 ==================== */
@media (max-width: 720px) {
    /* 1. 整体页面：压缩上下内边距，让内容紧贴顶部 */
    body { 
        padding: 2px 6px !important; 
        align-items: flex-start !important; 
    }

    /* 2. 主容器：纵向排列，彻底消除上下无效留白 */
    .sudoku-container {
        flex-direction: column;
        padding: 0 !important;
        gap: 4px !important; /* 模块之间的间距压到最小 */
        background: transparent;
        box-shadow: none;
        width: 100%;
        box-sizing: border-box;
    }

    /* 3. 顶部模式选择区域：贴顶显示 */
    .mode-selector, .tabs-container, .game-modes {
        margin-top: 0 !important;
        margin-bottom: 4px !important;
    }

    /* 4. 左右面板通栏 */
    .left-panel, .right-panel { 
        width: 100% !important; 
        max-width: 100% !important;
        padding: 0 !important;
        display: flex;
        flex-direction: column;
        align-items: center;
    }

    /* 5. 棋盘尺寸与紧随的下方间距 */
    .sudoku-board {
        width: 92vw !important;
        height: 92vw !important;
        max-width: 360px !important;
        max-height: 360px !important;
        margin-bottom: 2px !important; /* 🟢 极度拉近棋盘与下方状态栏的距离 */
    }

    /* 6. 状态栏和功能区宽度统一 */
    .status-bar, .game-info, .tools-bar, .action-tools, .secondary-controls, .numpad, .number-pad, .new-game-btn, .action-btn {
        width: 92vw !important;
        max-width: 360px !important;
        box-sizing: border-box;
    }

    /* 7. 内部各行组件的极简间距 */
    .status-bar, .game-info {
        margin: 2px 0 4px 0 !important;
    }

    .tools-bar, .action-tools, .secondary-controls {
        display: flex;
        justify-content: space-between;
        margin-bottom: 4px !important;
    }
    
    .numpad, .number-pad {
        display: flex;
        justify-content: space-between;
        margin-bottom: 8px !important; 
    }

    /* 8. 按钮高度及手感优化 */
    .num-btn {
        flex: 1;
        height: 44px;
        font-size: 19px;
        font-weight: bold;
    }
}