/* ============================================
   CSS Variables - 色彩系统
   ============================================ */
:root {
    /* 主色调 - 深蓝科技风 */
    --primary-dark: #0a1628;
    --primary-darker: #060d18;
    --primary-blue: #0d47a1;
    --primary-light: #1976d2;
    --accent-cyan: #00bcd4;
    --accent-purple: #7c4dff;

    /* 渐变 */
    --gradient-primary: linear-gradient(135deg, #0d47a1 0%, #1976d2 50%, #00bcd4 100%);
    --gradient-hero: linear-gradient(180deg, #0a1628 0%, #1a237e 100%);
    --gradient-card: linear-gradient(180deg, rgba(13,71,161,0.1) 0%, rgba(0,188,212,0.05) 100%);
    --gradient-text: linear-gradient(90deg, #00bcd4, #7c4dff);

    /* 文字颜色 */
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.7);
    --text-muted: rgba(255, 255, 255, 0.5);

    /* 功能色 */
    --success: #4caf50;
    --warning: #ff9800;
    --error: #f44336;

    /* 间距 */
    --section-padding: 100px;
    --container-padding: 24px;
    --container-max: 1200px;

    /* 圆角 */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.4);
    --shadow-glow: 0 0 40px rgba(0, 188, 212, 0.3);

    /* 过渡 */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;

    /* 字体 */
    --font-primary: 'Inter', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    --font-display: 'Orbitron', 'PingFang SC', sans-serif;
}

/* ============================================
   Reset & Base Styles
   ============================================ */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-primary);
    background-color: var(--primary-dark);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

ul {
    list-style: none;
}

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

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

input,
textarea,
select {
    font-family: inherit;
    font-size: inherit;
}

/* ============================================
   Typography
   ============================================ */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
}

h1 { font-size: 3.5rem; }
h2 { font-size: 2.625rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
p  { font-size: 1rem; color: var(--text-secondary); }

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

/* ============================================
   Layout
   ============================================ */
.container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--container-padding);
}

.section {
    padding: var(--section-padding) 0;
    position: relative;
    overflow: hidden;
}

.section-header {
    text-align: center;
    margin-bottom: 60px;
}

.section-header.left { text-align: left; }

.section-tag {
    display: inline-block;
    padding: 6px 16px;
    background: rgba(0, 188, 212, 0.15);
    border: 1px solid rgba(0, 188, 212, 0.3);
    border-radius: 20px;
    color: var(--accent-cyan);
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 16px;
}

.section-title {
    font-size: 2.625rem;
    font-weight: 700;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.section-desc {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 700px;
    margin: 0 auto;
}

.section-header.left .section-desc { margin: 0; }

/* ============================================
   Scroll Progress Bar
   ============================================ */
.scroll-progress {
    position: fixed;
    top: 0;
    left: 0;
    height: 3px;
    width: 0%;
    background: var(--gradient-primary);
    z-index: 9999;
    transition: width 0.1s linear;
}

/* ============================================
   Buttons
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 28px;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 0.9375rem;
    transition: all var(--transition-normal);
    cursor: pointer;
    border: none;
    text-decoration: none;
    white-space: nowrap;
    position: relative;
    overflow: hidden;
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 20px rgba(13, 71, 161, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 30px rgba(13, 71, 161, 0.6);
}

.btn-secondary {
    background: transparent;
    border: 2px solid rgba(255, 255, 255, 0.3);
    color: white;
}

.btn-secondary:hover {
    border-color: var(--accent-cyan);
    color: var(--accent-cyan);
}

.btn-lg {
    padding: 16px 36px;
    font-size: 1rem;
}

.btn-block { width: 100%; }

/* ============================================
   Responsive Typography
   ============================================ */
@media (max-width: 1024px) {
    h1 { font-size: 2.5rem; }
    h2 { font-size: 2rem; }
    .section-title { font-size: 2rem; }
    .section { padding: 70px 0; }
}

@media (max-width: 768px) {
    h1 { font-size: 2rem; }
    h2 { font-size: 1.75rem; }
    .section-title { font-size: 1.75rem; }
    .section { padding: 60px 0; }
    .section-desc { font-size: 1rem; }
}

@media (max-width: 480px) {
    h1 { font-size: 1.75rem; }
    h2 { font-size: 1.5rem; }
    .section-title { font-size: 1.5rem; }
    .container { padding: 0 16px; }
}