/* ===== CSS 变量 ===== */
:root {
    --breakpoint-mobile: 768px;
    --breakpoint-tablet: 1024px;
    --breakpoint-desktop: 1025px;

    --font-size-mobile: 16px;
    --font-size-tablet: 18px;
    --font-size-desktop: 18px;

    --transition-duration: 0.3s;
    --theme-transition: 0.1s;

    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-xxl: 3rem;

    --border-radius-sm: 4px;
    --border-radius-md: 8px;
    --border-radius-lg: 12px;
    --border-radius-round: 50%;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 20px rgba(0, 0, 0, 0.2);

    --z-index-dropdown: 100;
    --z-index-modal: 200;
    --z-index-toast: 300;
}

/* ===== 主题 ===== */
[data-theme="light"] {
    --bg-primary: #2C3E50;
    --bg-secondary: #34495E;
    --bg-card: rgba(161, 154, 154, 0.85);

    --text-primary: #3498DB;
    --text-secondary: #9B59B6;
    --text-accent: #5DADE2;

    --color-border: rgba(255, 255, 255, 0.3);
    --color-hover: #2980B9;

    --glass-blur: 12px;
    --glass-bg: rgba(218, 210, 210, 0.85);
    --glass-border: rgba(255, 255, 255, 0.3);
}

[data-theme="dark"] {
    --bg-primary: #000000;
    --bg-secondary: #1A1A1A;
    --bg-card: rgba(50, 50, 50, 0.85);

    --text-primary: #E74C3C;
    --text-secondary: #F1C40F;
    --text-accent: #C0392B;

    --color-border: rgba(255, 255, 255, 0.1);
    --color-hover: #D32F2F;

    --glass-blur: 12px;
    --glass-bg: rgba(50, 50, 50, 0.85);
    --glass-border: rgba(255, 255, 255, 0.1);
}

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

html {
    font-size: var(--font-size-mobile);
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    transition: background-color var(--theme-transition), color var(--theme-transition);
    min-height: 100vh;
    overflow-x: hidden;
}

a {
    color: inherit;
    text-decoration: none;
    transition: color var(--transition-duration);
}

a:hover {
    color: var(--color-hover);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

button {
    cursor: pointer;
    border: none;
    background: transparent;
    font-family: inherit;
    font-size: inherit;
    color: inherit;
}

ul, ol {
    list-style: none;
}

/* ===== 布局 ===== */
.header {
    position: sticky;
    top: 0;
    z-index: var(--z-index-dropdown);
    background: var(--glass-bg);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border-bottom: 1px solid var(--glass-border);
    padding: var(--spacing-md) var(--spacing-xl);
    transition: background var(--theme-transition);
}

.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1400px;
    margin: 0 auto;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    background: linear-gradient(135deg, var(--text-primary), var(--text-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-links {
    display: flex;
    gap: var(--spacing-lg);
}

.nav-link {
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius-md);
    transition: all var(--transition-duration);
}

.nav-link:hover {
    background: var(--bg-secondary);
}

.theme-toggle {
    padding: var(--spacing-sm);
    font-size: 1.5rem;
    border-radius: var(--border-radius-round);
    transition: transform var(--transition-duration);
}

.theme-toggle:hover {
    transform: rotate(180deg);
}

.main-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--spacing-xl);
    display: grid;
    gap: var(--spacing-xl);
}

.section {
    min-height: 400px;
}

.section-container {
    padding: var(--spacing-lg);
}

.footer {
    background: var(--glass-bg);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border-top: 1px solid var(--glass-border);
    padding: var(--spacing-lg);
    text-align: center;
    margin-top: auto;
}

.footer-content {
    max-width: 1400px;
    margin: 0 auto;
    color: var(--text-secondary);
}

/* ===== 响应式 ===== */
@media screen and (max-width: 767px) {
    html {
        font-size: var(--font-size-mobile);
    }

    .main-container {
        grid-template-columns: 1fr;
        padding: var(--spacing-md);
    }

    .nav-links {
        display: none;
    }

    .header {
        padding: var(--spacing-sm) var(--spacing-md);
    }

    .section-container {
        padding: var(--spacing-md);
    }
}

@media screen and (min-width: 768px) and (max-width: 1024px) {
    html {
        font-size: var(--font-size-tablet);
    }

    .main-container {
        grid-template-columns: repeat(2, 1fr);
    }

    .nav-links {
        display: flex;
    }
}

@media screen and (min-width: 1025px) {
    html {
        font-size: var(--font-size-desktop);
    }

    .main-container {
        grid-template-columns: repeat(3, 1fr);
    }

    .nav-links {
        display: flex;
    }
}

@media screen and (max-width: 320px) {
    body {
        overflow-x: scroll;
    }

    .main-container {
        min-width: 320px;
    }
}

@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

@media (hover: none) and (pointer: coarse) {
    .btn,
    .nav-link,
    .theme-toggle {
        min-height: 44px;
        min-width: 44px;
    }
}

@media (prefers-reduced-data: reduce) {
    img {
        max-resolution: 1x;
    }
}