/* ============================================
   RESET & GLOBAL STYLES
   ============================================ */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #2563eb;        /* 科技蓝 */
    --primary-dark: #1d4ed8;
    --secondary-color: #7c3aed;      /* 科技紫 */
    --accent-color: #06b6d4;         /* 科技青 */
    --dark-bg: #0f172a;              /* 深空蓝 */
    --dark-surface: #1e293b;
    --light-bg: #f8fafc;
    --light-surface: #ffffff;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-light: #f8fafc;
    --border-color: #e2e8f0;
    --border-radius: 12px;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15);
    --shadow-glow: 0 0 15px rgba(37, 99, 235, 0.2);
    --gradient-primary: linear-gradient(135deg, #2563eb 0%, #7c3aed 100%);
    --gradient-dark: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    line-height: 1.7;
    color: var(--text-primary);
    background-color: var(--light-bg);
    padding: 20px;
    max-width: 1200px;
    margin: 0 auto;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ============================================
   TYPOGRAPHY
   ============================================ */
h1, h2, h3, h4 {
    font-weight: 600;
    line-height: 1.2;
    letter-spacing: -0.025em;
}

h1 {
    font-size: 2.8rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
    margin-bottom: 0.5rem;
}

h2 {
    font-size: 1.8rem;
    color: var(--text-primary);
    margin-bottom: 1.5rem;
    position: relative;
    display: inline-block;
}

h2::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    width: 50px;
    height: 4px;
    background: var(--gradient-primary);
    border-radius: 2px;
}

h3 {
    font-size: 1.3rem;
    color: var(--text-primary);
    margin-bottom: 0.8rem;
}

.tagline {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-weight: 400;
    letter-spacing: 0.02em;
}

/* ============================================
   HEADER STYLES
   ============================================ */
header {
    text-align: center;
    padding: 3rem 2rem;
    margin-bottom: 3rem;
    background: var(--light-surface);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    position: relative;
    overflow: hidden;
}

header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
}

/* ============================================
   NAVIGATION STYLES
   ============================================ */
nav {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    gap: 1.5rem;
    padding: 1.2rem;
    margin-top: 1.5rem;
    background: var(--light-surface);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

nav a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 0;
    position: relative;
    transition: var(--transition);
}

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

nav a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--gradient-primary);
    transition: var(--transition);
}

nav a:hover::after {
    width: 100%;
}

/* ============================================
   LANGUAGE SWITCHER
   ============================================ */
.language-switcher {
    margin-left: auto;
}

.language-select {
    padding: 0.6rem 2.5rem 0.6rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--light-surface);
    color: var(--text-primary);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    min-width: 140px;
    appearance: none;
    -webkit-appearance: none;
    -moz-appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%232563eb' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    background-size: 16px;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.language-select:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-glow);
}

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

/* ============================================
   CONTENT BOXES
   ============================================ */
.content-box {
    background: var(--light-surface);
    padding: 2.5rem;
    margin-bottom: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: var(--transition);
}

.content-box:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
}

.service-box {
    border-left: 4px solid var(--primary-color);
    position: relative;
}

/* ============================================
   SERVICE STYLES
   ============================================ */
.service {
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.service:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.service h3 {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.service h3::before {
    content: '';
    display: inline-block;
    width: 8px;
    height: 8px;
    background: var(--primary-color);
    border-radius: 50%;
}

/* ============================================
   LISTS STYLES
   ============================================ */
ul {
    padding-left: 1.5rem;
    margin: 1rem 0;
}

li {
    margin-bottom: 0.8rem;
    padding-left: 0.5rem;
    position: relative;
}

li::before {
    content: '→';
    position: absolute;
    left: -1.2rem;
    color: var(--primary-color);
    font-weight: bold;
}

li strong {
    color: var(--primary-color);
    font-weight: 600;
}

/* ============================================
   FOOTER STYLES
   ============================================ */
footer {
    text-align: center;
    padding: 2.5rem;
    margin-top: 4rem;
    background: var(--dark-surface);
    color: var(--text-light);
    border-radius: var(--border-radius);
    border-top: 4px solid var(--primary-color);
}

footer a {
    color: var(--accent-color);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

footer a:hover {
    color: #ffffff;
}

footer a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 1px;
    background: var(--accent-color);
    transition: var(--transition);
}

footer a:hover::after {
    width: 100%;
}

/* ============================================
   UTILITY CLASSES
   ============================================ */
.highlight {
    color: var(--primary-color);
    font-weight: 600;
}

.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */
@media (max-width: 768px) {
    body {
        padding: 1rem;
    }
    
    header {
        padding: 2rem 1rem;
        margin-bottom: 2rem;
    }
    
    h1 {
        font-size: 2.2rem;
    }
    
    h2 {
        font-size: 1.5rem;
    }
    
    nav {
        flex-direction: column;
        gap: 1rem;
        padding: 1.5rem;
    }
    
    .language-switcher {
        margin-left: 0;
        width: 100%;
    }
    
    .language-select {
        width: 100%;
        max-width: 100%;
    }
    
    .content-box {
        padding: 1.5rem;
    }
    
    footer {
        padding: 2rem 1.5rem;
    }
}

@media (max-width: 480px) {
    h1 {
        font-size: 1.8rem;
    }
    
    h2 {
        font-size: 1.3rem;
    }
    
    .tagline {
        font-size: 1rem;
    }
    
    .content-box {
        padding: 1.2rem;
    }
}

/* ============================================
   ANIMATIONS
   ============================================ */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.content-box {
    animation: fadeIn 0.6s ease-out;
}

/* ============================================
   DARK MODE (OPTIONAL)
   ============================================ */
@media (prefers-color-scheme: dark) {
    body {
        background-color: var(--dark-bg);
        color: var(--text-light);
    }
    
    header,
    nav,
    .content-box {
        background-color: var(--dark-surface);
        border-color: #334155;
    }
    
    h2, h3 {
        color: var(--text-light);
    }
    
    .tagline {
        color: #cbd5e1;
    }
    
    nav a {
        color: #cbd5e1;
    }
    
    .language-select {
        background-color: var(--dark-surface);
        color: var(--text-light);
        border-color: #334155;
        background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%23cbd5e1' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    }
    
    li::before {
        color: var(--accent-color);
    }
}