/* ========================================
   Tiyi1.com - AI大模型学习网
   航天科技风全局样式
   ======================================== */

/* CSS Reset & 基础变量 */
:root {
    --space-black: #0a0b10;
    --deep-space: #0f111a;
    --star-white: #f5f7fa;
    --light-purple: #b8a9d6;
    --purple-glow: #9d7cd8;
    --neon-blue: #4fc3f7;
    --tech-cyan: #26c6da;
    --gradient-primary: linear-gradient(135deg, #0f111a 0%, #1a1d2e 50%, #0f111a 100%);
    --gradient-accent: linear-gradient(90deg, #9d7cd8, #4fc3f7);
    --shadow-glow: 0 0 20px rgba(157, 124, 216, 0.3);
    --border-tech: 1px solid rgba(157, 124, 216, 0.2);
    --transition-smooth: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

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

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

body {
    font-family: 'Segoe UI', 'Microsoft YaHei', 'PingFang SC', sans-serif;
    background-color: var(--space-black);
    color: var(--star-white);
    line-height: 1.7;
    overflow-x: hidden;
    position: relative;
}

body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(circle at 20% 30%, rgba(157, 124, 216, 0.08) 0%, transparent 50%),
        radial-gradient(circle at 80% 70%, rgba(79, 195, 247, 0.06) 0%, transparent 50%);
    pointer-events: none;
    z-index: -1;
}

/* 滚动条美化 */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--deep-space);
}

::-webkit-scrollbar-thumb {
    background: var(--purple-glow);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--neon-blue);
}

/* 链接基础样式 */
a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition-smooth);
}

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

/* 图片响应式 */
img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* ========================================
   顶部导航栏
   ======================================== */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    padding: 1rem 5%;
    background: transparent;
    transition: var(--transition-smooth);
    backdrop-filter: blur(10px);
}

.site-header.scrolled {
    background: rgba(15, 17, 26, 0.95);
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.3);
    border-bottom: var(--border-tech);
}

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

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: 2px;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2.5rem;
}

.nav-link {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--star-white);
    position: relative;
    padding: 0.5rem 0;
}

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

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.nav-link:hover,
.nav-link.active {
    color: var(--neon-blue);
}

/* 汉堡菜单 */
.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 5px;
}

.hamburger span {
    width: 28px;
    height: 3px;
    background: var(--star-white);
    transition: var(--transition-smooth);
}

.hamburger.active span:nth-child(1) {
    transform: rotate(45deg) translate(6px, 6px);
}

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: rotate(-45deg) translate(6px, -6px);
}

/* ========================================
   页脚
   ======================================== */
.site-footer {
    background: var(--deep-space);
    padding: 4rem 5% 2rem;
    border-top: var(--border-tech);
}

.footer-container {
    max-width: 1400px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 3rem;
}

.footer-section h4 {
    font-size: 1.2rem;
    margin-bottom: 1.5rem;
    color: var(--light-purple);
    position: relative;
    padding-bottom: 0.5rem;
}

.footer-section h4::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 40px;
    height: 2px;
    background: var(--gradient-accent);
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: 0.8rem;
}

.footer-links a {
    color: var(--star-white);
    opacity: 0.8;
}

.footer-links a:hover {
    opacity: 1;
    color: var(--neon-blue);
}

.contact-info p {
    margin-bottom: 0.8rem;
    opacity: 0.8;
}

.footer-bottom {
    max-width: 1400px;
    margin: 3rem auto 0;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
    opacity: 0.7;
    font-size: 0.9rem;
}

/* ========================================
   通用组件
   ======================================== */
.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 5%;
}

.section-title {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 1rem;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-subtitle {
    text-align: center;
    color: var(--light-purple);
    font-size: 1.1rem;
    margin-bottom: 3rem;
    opacity: 0.8;
}

.btn {
    display: inline-block;
    padding: 1rem 2.5rem;
    background: var(--gradient-accent);
    color: var(--space-black);
    font-weight: 600;
    border-radius: 50px;
    transition: var(--transition-smooth);
    border: none;
    cursor: pointer;
}

.btn:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-glow);
    color: var(--space-black);
}

.btn-outline {
    background: transparent;
    border: 2px solid var(--purple-glow);
    color: var(--star-white);
}

.btn-outline:hover {
    background: var(--purple-glow);
    color: var(--space-black);
}

/* 卡片样式 */
.card {
    background: rgba(255, 255, 255, 0.03);
    border: var(--border-tech);
    border-radius: 16px;
    padding: 2rem;
    transition: var(--transition-smooth);
    backdrop-filter: blur(10px);
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-glow);
    border-color: var(--purple-glow);
}

/* ========================================
   动画效果
   ======================================== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(40px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.6;
    }
}

.animate-on-scroll {
    opacity: 0;
    transform: translateY(40px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.animate-on-scroll.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ========================================
   响应式设计
   ======================================== */
@media (max-width: 992px) {
    .nav-menu {
        position: fixed;
        top: 70px;
        right: -100%;
        width: 280px;
        height: calc(100vh - 70px);
        background: var(--deep-space);
        flex-direction: column;
        padding: 2rem;
        gap: 1.5rem;
        transition: var(--transition-smooth);
        border-left: var(--border-tech);
    }

    .nav-menu.active {
        right: 0;
    }

    .hamburger {
        display: flex;
    }

    .section-title {
        font-size: 2rem;
    }
}

@media (max-width: 768px) {
    html {
        font-size: 14px;
    }

    .header-container {
        padding: 0 1rem;
    }

    .footer-container {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .card {
        padding: 1.5rem;
    }
}

@media (max-width: 480px) {
    .logo {
        font-size: 1.4rem;
    }

    .btn {
        padding: 0.8rem 1.8rem;
        font-size: 0.9rem;
    }
}