:root {
    --primary-color: #4a90e2;
    --accent-color: #50e3c2;
    --bg-color: #f5f7fa;
    --board-bg: #ffffff;
    --border-color: #333;
    --light-border: #ccc;
    --highlight-bg: #e2eafc;
    --error-color: #e74c3c;
    --fixed-text: #2c3e50;
    --user-text: #4a90e2;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* body 背景、字体继承全局 style.css，此处不再覆盖 */

/* 卡片：与其它工具页白底圆角阴影风格一致 */
.card {
    background: #fff;
    border-radius: var(--border-radius, 12px);
    padding: 24px;
    margin-top: 20px;
    box-shadow: var(--shadow, 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06));
}

/* 移动端：收紧卡片 padding 与间距，与全局断点一致 */
@media (max-width: 600px) {
    .card {
        padding: 16px;
        margin-top: 16px;
    }

    /* 键盘卡片紧贴棋盘 */
    .numpad-container.card {
        margin-top: 12px;
    }

    .controls-section {
        padding: 12px;
        gap: 12px;
    }

    .rules-section h2 {
        font-size: 1.05rem;
    }

    .rules-section ul {
        padding-left: 18px;
        line-height: 1.7;
    }
}

/* 标题颜色随全局深色 */
header h1 {
    color: inherit;
}

.app-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

header {
    text-align: center;
    margin-bottom: 20px;
}

h1 {
    color: var(--primary-color);
}

/* 控制区 - 优化布局 */
.controls-section {
    width: 100%;
    max-width: 600px; /* 限制宽度 */
    margin: 0 auto; /* 居中 */
    background: transparent;
    padding: 15px 20px;
    border-radius: 8px;
    box-shadow: none;
    display: flex;
    flex-wrap: wrap;
    justify-content: center; /* 居中对齐 */
    align-items: center;
    gap: 15px; /* 增加间距 */
}

.difficulty-selector {
    display: flex;
    align-items: center;
    gap: 10px;
}

.difficulty-selector select {
    padding: 8px 12px;
    border-radius: 4px;
    border: 1px solid var(--light-border);
    font-size: 1rem;
    cursor: pointer;
}

.action-buttons {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    justify-content: center;
}

button {
    padding: 8px 16px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.95rem;
    transition: background-color 0.2s;
}

.primary-btn {
    background-color: var(--primary-color);
    color: white;
}
.primary-btn:hover { background-color: #357abd; }

.secondary-btn {
    background-color: #e0e0e0;
    color: #333;
}
.secondary-btn:hover { background-color: #d0d0d0; }

.accent-btn {
    background-color: var(--accent-color);
    color: #004d40;
}
.accent-btn:hover { background-color: #3dd1b0; }

/* 规则说明列表 */
.rules-section h2 {
    font-size: 1.2rem;
    font-weight: 600;
    color: #374151;
    margin-bottom: 12px;
}
.rules-section ul {
    list-style: disc;
    padding-left: 20px;
    line-height: 1.8;
    color: #4b5563;
}
.rules-section li {
    margin-bottom: 4px;
}

/* 游戏棋盘 */
.game-board-container {
    display: flex;
    justify-content: center;
    max-width: 540px; /* 匹配棋盘宽度 + 卡片 padding */
    margin-left: auto;
    margin-right: auto;
}

.sudoku-board {
    display: grid;
    /* 自适应卡片内容区宽度，保持正方形，格子等分 */
    width: 100%;
    max-width: 480px;
    aspect-ratio: 1 / 1;
    grid-template-columns: repeat(9, 1fr);
    grid-template-rows: repeat(9, 1fr);
    border: 3px solid #333; /* 外框加深 */
    background-color: #333; /* 宫格线颜色 */
    gap: 1px;
    border-radius: 12px; /* 四角圆角，与卡片一致 */
    overflow: hidden; /* 裁剪内部格子直角，贴合圆角 */
    box-shadow: 0 5px 15px rgba(0,0,0,0.15); /* 立体阴影 */
}

.cell {
    background-color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: clamp(1rem, 4vw, 1.3rem); /* 字号随屏宽缩放 */
    cursor: pointer;
    user-select: none;
    position: relative;
}

/* 3x3 宫格粗边框 - 覆盖 */
.cell.border-right {
    border-right: 2px solid #333 !important;
}
.cell.border-bottom {
    border-bottom: 2px solid #333 !important;
}

/* 选中状态 */
.cell.selected {
    background-color: var(--highlight-bg) !important;
    box-shadow: inset 0 0 0 2px var(--primary-color); /* 内阴影高亮 */
}

/* 相同数字高亮 */
.cell.highlight-same {
    background-color: #d6eaf8;
}

/* 关联格子高亮（行、列、宫格） */
.cell.highlight-related {
    background-color: #e8f4fd;
}

/* 错误状态 */
.cell.error {
    color: var(--error-color) !important;
    background-color: #fadbd8;
}

/* 固定数字样式 */
.cell.fixed {
    color: var(--fixed-text);
    font-weight: bold;
}

/* 用户输入数字样式 */
.cell:not(.fixed) {
    color: var(--user-text);
}

/* 键盘区 - 居中限宽，紧贴棋盘 */
.numpad-container {
    display: grid;
    grid-template-columns: repeat(5, 1fr); /* 等分自适应，避免窄屏溢出 */
    justify-content: center;
    gap: 8px;
    margin: 0 auto;
    width: 100%;
    max-width: 320px;
}

/* 键盘卡片紧贴上方棋盘 */
.numpad-container.card {
    margin-top: 12px;
}

.num-btn {
    aspect-ratio: 1 / 1;
    font-size: 1.2rem;
    background-color: white;
    border: 1px solid var(--light-border);
    border-radius: 6px;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.1s;
}

.num-btn:hover {
    border-color: var(--primary-color);
    background-color: #f0f7ff;
}

.num-btn:active {
    background-color: var(--highlight-bg);
    transform: scale(0.95);
}

.num-btn[data-val="clear"] {
    font-size: 0.85rem;
    color: #e74c3c;
}

/* 预置数字 */
.modal {
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background-color: rgba(0,0,0,0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 2000; /* 提高层级 */
}
.modal.hidden {
    display: none !important;
}

.modal-content {
    background: white;
    padding: 20px;
    border-radius: 8px;
    width: 90%;
    max-width: 400px;
    position: relative;
}
.close-modal {
    position: absolute;
    top: 10px; right: 15px;
    font-size: 1.5rem;
    cursor: pointer;
}
.print-settings {
    margin: 20px 0;
}
.setting-item {
    display: flex;
    justify-content: space-between;
    margin-bottom: 10px;
    align-items: center;
}
.setting-item select,
.setting-item input[type="number"] {
    padding: 8px 12px;
    border: 1px solid #d1d5db;
    border-radius: 6px;
    background-color: white;
    font-size: 0.95rem;
    color: #1f2937;
    min-width: 100px;
    cursor: pointer;
}

.setting-item select:focus,
.setting-item input[type="number"]:focus {
    border-color: var(--primary-color);
    outline: 2px solid rgba(37, 99, 235, 0.1);
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
}

/* 打印专用区域 (屏幕隐藏，打印显示) */
#print-area {
    display: none;
}
.print-only {
    display: none;
}

@media print {
    @page {
        size: A4;
        margin: 10mm;
    }
    
    body {
        background-color: white;
        color: black;
        -webkit-print-color-adjust: exact;
        print-color-adjust: exact;
    }

    .no-print {
        display: none !important;
    }

    #print-area, .print-only {
        display: block !important;
        width: 100%;
        height: 100%;
    }

    .print-page {
        width: 100%;
        min-height: 270mm; 
        display: grid;
        justify-content: center;
        align-content: start;
        page-break-after: always;
        gap: 10mm;
    }

    .print-item {
        display: flex;
        flex-direction: column;
        align-items: center;
        page-break-inside: avoid;
    }

    .print-title {
        font-size: 16pt;
        margin-bottom: 5mm;
        font-weight: bold;
        font-family: "DengXian", "Microsoft YaHei", sans-serif;
        text-align: center;
    }

    .print-board {
        display: grid;
        grid-template-columns: repeat(9, 1fr);
        border: 3px solid #000;
        background: transparent;
    }

    /* 布局适配 (保留修正后的尺寸，确保打印成功) */
    
    /* 1个/页 */
    .print-layout-1 {
        align-content: center;
    }
    .print-layout-1 .print-board {
        width: 16cm;
        height: 16cm;
    }
    .print-layout-1 .print-cell {
        font-size: 24pt;
    }

    /* 2个/页 */
    .print-layout-2 {
        grid-template-columns: 1fr;
        grid-template-rows: auto auto;
        align-content: center;
        gap: 10mm;
    }
    .print-layout-2 .print-board {
        width: 10.5cm; /* 修正后的尺寸 */
        height: 10.5cm;
    }
    .print-layout-2 .print-cell {
        font-size: 16pt;
    }

    /* 4个/页 */
    .print-layout-4 {
        grid-template-columns: 1fr 1fr;
        grid-template-rows: auto auto;
        gap: 10mm;
        align-content: center;
        justify-items: center;
    }
    .print-layout-4 .print-board {
        width: 8cm; 
        height: 8cm;
        border-width: 2px;
    }
    .print-layout-4 .print-title {
        font-size: 12pt;
        margin-bottom: 2mm;
    }
    .print-layout-4 .print-cell {
        font-size: 12pt;
    }

    /* 单元格样式 */
    .print-cell {
        border: 0.5pt solid #000; /* 内部线条变细，使用 pt 单位 */
        display: flex;
        align-items: center;
        justify-content: center;
        position: relative;
        background: transparent !important;
    }

    .print-cell.border-right { 
        border-right: 3px solid #000 !important; 
    }
    .print-cell.border-bottom { 
        border-bottom: 3px solid #000 !important; 
    }
    
    .print-cell-content {
        font-family: "DengXian", sans-serif;
        font-weight: 600;
        color: #000;
    }
}