/* 导入中文字体 - 使用国内CDN */
@import url('https://fonts.lug.ustc.edu.cn/css2?family=Noto+Sans+SC:wght@400;500;700&display=swap');

/* CSS变量 - 设计系统 */
:root {
    /* 主色调 */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);

    /* 背景色 */
    --bg-dark: #0f0c29;
    --bg-medium: #1a1a2e;
    --bg-light: #16213e;

    /* 文字颜色 */
    --text-primary: #ffffff;
    --text-secondary: #b8b8d1;
    --text-accent: #667eea;

    /* 单元格颜色 */
    --cell-bg: rgba(255, 255, 255, 0.05);
    --cell-border: rgba(255, 255, 255, 0.1);
    --cell-hover: rgba(102, 126, 234, 0.2);
    --cell-selected: rgba(102, 126, 234, 0.3);
    --cell-filled: rgba(255, 255, 255, 0.08);
    --cell-error: rgba(245, 87, 108, 0.3);
    --cell-correct: rgba(0, 242, 254, 0.2);

    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 20px rgba(102, 126, 234, 0.3);

    /* 边框半径 */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;

    /* 过渡 */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* 全局样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-dark);
    background-image:
        radial-gradient(circle at 20% 50%, rgba(102, 126, 234, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(118, 75, 162, 0.1) 0%, transparent 50%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    color: var(--text-primary);
}

.container {
    max-width: 600px;
    width: 100%;
}

/* 标题区域 */
.header {
    text-align: center;
    margin-bottom: 16px;
    animation: fadeInDown 0.6s ease;
}

.title {
    font-size: 2rem;
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 6px;
    text-shadow: var(--shadow-glow);
    letter-spacing: 1px;
}

.subtitle {
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-weight: 400;
}

/* 信息栏 */
.info-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--cell-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-md);
    padding: 10px 14px;
    margin-bottom: 12px;
    box-shadow: var(--shadow-md);
}

.difficulty-display,
.timer-display {
    display: flex;
    align-items: center;
    gap: 8px;
}

.label {
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.value {
    color: var(--text-primary);
    font-weight: 600;
    font-size: 0.95rem;
}

.icon-btn {
    background: transparent;
    border: none;
    cursor: pointer;
    font-size: 1.3rem;
    padding: 2px;
    transition: transform var(--transition-fast);
}

.icon-btn:hover {
    transform: scale(1.1);
}

.icon-btn:active {
    transform: scale(0.95);
}

.sound-icon {
    display: inline-block;
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.3));
}

.sound-icon::before {
    content: '🔊';
}

/* 难度选择器 */
.difficulty-selector {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
    margin-bottom: 12px;
    animation: fadeIn 0.6s ease 0.2s both;
}

.difficulty-btn {
    padding: 10px 16px;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 600;
    font-family: 'Noto Sans SC', sans-serif;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-sm);
    position: relative;
    overflow: hidden;
}

.difficulty-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    transform: translateX(-100%);
    transition: transform 0.6s;
}

.difficulty-btn:hover::before {
    transform: translateX(100%);
}

.difficulty-btn.easy {
    background: linear-gradient(135deg, #84fab0 0%, #8fd3f4 100%);
    color: #1a1a2e;
}

.difficulty-btn.medium {
    background: linear-gradient(135deg, #ffa751 0%, #ffe259 100%);
    color: #1a1a2e;
}

.difficulty-btn.hard {
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    color: #ffffff;
}

.difficulty-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.difficulty-btn:active {
    transform: translateY(0);
}

/* 游戏容器 */
.game-container {
    margin-bottom: 12px;
    animation: fadeIn 0.6s ease 0.3s both;
}

/* 数独网格 */
.sudoku-grid {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 0;
    background: var(--bg-light);
    border-radius: var(--radius-lg);
    padding: 8px;
    box-shadow: var(--shadow-lg);
    border: 2px solid rgba(102, 126, 234, 0.3);
}

.cell {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--cell-bg);
    border: 1px solid var(--cell-border);
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
}

/* 3x3宫格分隔 */
.cell:nth-child(9n+3),
.cell:nth-child(9n+6) {
    border-right: 2px solid rgba(102, 126, 234, 0.4);
}

.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
    border-bottom: 2px solid rgba(102, 126, 234, 0.4);
}

/* 圆角处理 */
.cell:nth-child(1) {
    border-top-left-radius: 8px;
}

.cell:nth-child(9) {
    border-top-right-radius: 8px;
}

.cell:nth-child(73) {
    border-bottom-left-radius: 8px;
}

.cell:nth-child(81) {
    border-bottom-right-radius: 8px;
}

.cell:hover:not(.fixed) {
    background: var(--cell-hover);
    transform: scale(1.05);
    z-index: 1;
}

.cell.selected {
    background: var(--cell-selected);
    box-shadow: inset 0 0 0 2px rgba(102, 126, 234, 0.6);
    z-index: 2;
}

.cell.fixed {
    background: var(--cell-filled);
    color: var(--text-accent);
    cursor: default;
    font-weight: 700;
}

.cell.highlight {
    background: rgba(102, 126, 234, 0.15);
}

/* 数字输入面板 */
.number-pad {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 6px;
    margin-bottom: 12px;
    animation: fadeIn 0.6s ease 0.4s both;
}

.number-btn {
    padding: 12px;
    background: var(--cell-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--cell-border);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1.1rem;
    font-weight: 600;
    font-family: 'Noto Sans SC', sans-serif;
    cursor: pointer;
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-sm);
}

.number-btn:hover {
    background: var(--cell-hover);
    border-color: rgba(102, 126, 234, 0.5);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.number-btn:active {
    transform: translateY(0);
}

.clear-btn {
    background: linear-gradient(135deg, rgba(245, 87, 108, 0.3), rgba(240, 147, 251, 0.2));
    border-color: rgba(245, 87, 108, 0.4);
}

/* 控制按钮 */
.controls {
    display: grid;
    grid-template-columns: 1fr;
    gap: 8px;
    margin-bottom: 12px;
    animation: fadeIn 0.6s ease 0.5s both;
}

/* 辅助功能按钮 */
.helper-controls {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
    animation: fadeIn 0.6s ease 0.55s both;
}

.helper-btn {
    padding: 10px 16px;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 600;
    font-family: 'Noto Sans SC', sans-serif;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-sm);
    background: var(--cell-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--cell-border);
    color: var(--text-primary);
}

.helper-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: rgba(102, 126, 234, 0.5);
}

.helper-btn:active {
    transform: translateY(0);
}

.control-btn {
    padding: 10px 16px;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 600;
    font-family: 'Noto Sans SC', sans-serif;
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-sm);
}

.control-btn.primary {
    background: var(--primary-gradient);
    color: var(--text-primary);
}

.control-btn.secondary {
    background: var(--cell-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--cell-border);
    color: var(--text-primary);
}

.control-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.control-btn.primary:hover {
    box-shadow: var(--shadow-glow);
}

.control-btn:active {
    transform: translateY(0);
}

/* 消息提示 */
.message {
    margin-top: 12px;
    padding: 12px 16px;
    border-radius: var(--radius-md);
    text-align: center;
    font-size: 0.9rem;
    font-weight: 600;
    box-shadow: var(--shadow-md);
    animation: slideUp 0.3s ease;
}

.message.success {
    background: linear-gradient(135deg, rgba(79, 172, 254, 0.3), rgba(0, 242, 254, 0.3));
    border: 1px solid rgba(0, 242, 254, 0.5);
}

.message.error {
    background: linear-gradient(135deg, rgba(245, 87, 108, 0.3), rgba(240, 147, 251, 0.3));
    border: 1px solid rgba(245, 87, 108, 0.5);
}

.message.info {
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.3), rgba(118, 75, 162, 0.3));
    border: 1px solid rgba(102, 126, 234, 0.5);
}

.message.hidden {
    display: none;
}

/* 动画 */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

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

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }

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

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

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



/* 响应式设计 */
@media (max-width: 640px) {
    .title {
        font-size: 1.5rem;
    }

    .cell {
        font-size: 1rem;
    }

    .number-btn {
        padding: 10px;
        font-size: 1rem;
    }

    .difficulty-btn,
    .control-btn,
    .helper-btn {
        padding: 8px 12px;
        font-size: 0.85rem;
    }
}