:root {
    /* 浅色极简 Blue 主题 */
    --bg-color: #f8fafc;           /* 极浅蓝灰背景 */
    --card-bg: #ffffff;            /* 纯白卡片 */
    --text-primary: #334155;       /* 深蓝灰文字 */
    --text-secondary: #64748b;     /* 浅蓝灰文字 */
    --accent-color: #2563eb;       /* 标准蓝 */
    --accent-hover: #1d4ed8;       /* 深蓝悬停 */
    --accent-light: #eff6ff;       /* 浅蓝背景 */
    --border-color: #e2e8f0;       /* 浅灰边框 */
    --success: #10b981;
    --danger: #ef4444;
    
    /* 通用间距 */
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 2rem;
    
    /* 圆角 - 更柔和 */
    --radius-md: 12px;
    --radius-lg: 24px;
    
    /* 阴影 - 更轻盈 */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -1px rgba(0, 0, 0, 0.03);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.05), 0 4px 6px -2px rgba(0, 0, 0, 0.03);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
    flex: 1;
    width: 100%;
}

/* 头部样式 */
header {
    text-align: center;
    margin-bottom: 4rem;
    padding-bottom: 2rem;
    position: relative;
}

header::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 4px;
    background: var(--accent-color);
    border-radius: 2px;
}

h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
    font-weight: 800;
    letter-spacing: -0.5px;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    font-weight: 400;
}

/* 卡片网格 */
.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2.5rem;
    margin-bottom: 4rem;
}

/* 工具卡片 */
.tool-card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2.5rem 2rem;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    text-decoration: none;
    color: var(--text-primary);
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    text-align: left;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
}

.tool-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--accent-color);
}

.tool-icon-box {
    width: 64px;
    height: 64px;
    border-radius: 16px;
    background: var(--accent-light);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1.5rem;
    color: var(--accent-color);
}

.tool-icon-svg {
    width: 32px;
    height: 32px;
}

.tool-card h2 {
    margin-bottom: 0.8rem;
    font-size: 1.4rem;
    font-weight: 700;
}

.tool-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.6;
}

.tool-card.coming-soon {
    opacity: 0.6;
    cursor: not-allowed;
    background-color: #f9fafb;
}

.tool-card.coming-soon:hover {
    transform: none;
    box-shadow: var(--shadow-sm);
    border-color: var(--border-color);
}

/* 导航栏 (用于内页) */
.nav-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.2rem 2rem;
    background-color: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    margin-bottom: 2rem;
}

.nav-brand {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--text-primary);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 0.8rem;
}

.nav-back {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    transition: all 0.2s;
}

.nav-back:hover {
    color: var(--accent-color);
    background: var(--accent-light);
}

/* 按钮通用样式 */
.btn {
    padding: 0.8rem 1.5rem;
    border-radius: var(--radius-md);
    border: none;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    font-size: 0.95rem;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.btn-primary {
    background-color: var(--accent-color);
    color: white;
    box-shadow: 0 2px 4px rgba(37, 99, 235, 0.2);
}

.btn-primary:hover {
    background-color: var(--accent-hover);
    box-shadow: 0 4px 8px rgba(37, 99, 235, 0.3);
    transform: translateY(-1px);
}

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

.btn-outline {
    background: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
}

.btn-outline:hover {
    border-color: var(--text-primary);
    color: var(--text-primary);
    background: white;
}

/* 输入框通用样式 */
input[type="text"], 
input[type="number"],
select {
    background-color: white;
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.8rem 1rem;
    border-radius: var(--radius-md);
    width: 100%;
    font-size: 0.95rem;
    transition: all 0.2s;
    box-shadow: 0 1px 2px rgba(0,0,0,0.02);
}

input:focus, select:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

input:disabled {
    background-color: #f1f5f9;
    cursor: not-allowed;
}

/* 底部 */
footer {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
    border-top: 1px solid var(--border-color);
    background: white;
    margin-top: auto; /* 沉底关键 */
}

footer p {
    margin: 0.5rem 0;
}

/* 响应式适配 */
@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }
    
    .container {
        padding: 1rem;
    }
    
    .tools-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }
    
    .tool-card {
        padding: 1.5rem;
    }
}