/* ============================================
   张美德 - AI全栈工程师 | 个人介绍网站
   设计风格：暗色主题 + 蓝色科技风
   ============================================ */

/* --- CSS Variables 主题系统 --- */
:root {
    --color-primary: #2563EB;
    --color-primary-dark: #1D4ED8;
    --color-primary-light: #3B82F6;
    --color-accent: #06B6D4;
    --color-accent-glow: rgba(6, 182, 212, 0.3);
    --color-bg: #0F172A;
    --color-bg-secondary: #1E293B;
    --color-bg-card: #1E293B;
    --color-bg-card-hover: #273548;
    --color-bg-light: #334155;
    --color-border: #334155;
    --color-text: #F1F5F9;
    --color-text-secondary: #CBD5E1;
    --color-text-muted: #94A3B8;
    --color-success: #10B981;
    --color-warning: #F59E0B;
    --color-error: #EF4444;
    --font-sans: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    --font-mono: 'Cascadia Code', 'Fira Code', 'JetBrains Mono', monospace;
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    --max-width: 1200px;
    --nav-height: 70px;
}

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--nav-height);
}

body {
    font-family: var(--font-sans);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.7;
    overflow-x: hidden;
}

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

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

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

/* --- Utility --- */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 24px;
}

.section {
    padding: 100px 0;
}

.section-title {
    font-size: 32px;
    font-weight: 700;
    text-align: center;
    margin-bottom: 16px;
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 3px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    margin: 16px auto 0;
    border-radius: 2px;
}

.section-subtitle {
    text-align: center;
    color: var(--color-text-muted);
    font-size: 16px;
    margin-bottom: 60px;
}

/* ============================================
   Navigation 导航栏
   ============================================ */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background: rgba(15, 23, 42, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(51, 65, 85, 0.5);
    z-index: 1000;
    transition: background var(--transition-normal), box-shadow var(--transition-normal);
}

.nav.scrolled {
    background: rgba(15, 23, 42, 0.95);
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.3);
}

.nav .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
}

.nav-logo {
    font-size: 20px;
    font-weight: 700;
    color: var(--color-text);
    letter-spacing: 1px;
}

.nav-logo span {
    color: var(--color-primary-light);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 32px;
}

.nav-links a {
    color: var(--color-text-muted);
    font-size: 15px;
    font-weight: 500;
    padding: 8px 0;
    position: relative;
    transition: color var(--transition-fast);
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--color-primary);
    transition: width var(--transition-normal);
    border-radius: 1px;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--color-text);
}

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

/* ============================================
   Hero Section 首屏
   ============================================ */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    position: relative;
    overflow: hidden;
}

/* 粒子背景 */
#particles-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
}

.hero .container {
    position: relative;
    z-index: 1;
}

.hero-content {
    text-align: center;
    max-width: 800px;
    margin: 0 auto;
}

.hero-greeting {
    font-size: 18px;
    color: var(--color-accent);
    font-family: var(--font-mono);
    margin-bottom: 20px;
    opacity: 0;
    animation: fadeInUp 0.8s ease forwards;
}

.hero-name {
    font-size: 56px;
    font-weight: 800;
    background: linear-gradient(135deg, var(--color-text) 0%, var(--color-primary-light) 50%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 20px;
    opacity: 0;
    animation: fadeInUp 0.8s ease 0.2s forwards;
}

.hero-role {
    font-size: 22px;
    font-weight: 500;
    color: var(--color-text-secondary);
    margin-bottom: 12px;
    min-height: 33px;
}

.hero-role .cursor {
    display: inline-block;
    width: 2px;
    height: 24px;
    background: var(--color-primary-light);
    margin-left: 4px;
    vertical-align: text-bottom;
    animation: blink 0.8s infinite;
}

.hero-tags {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 12px;
    margin-bottom: 40px;
    opacity: 0;
    animation: fadeInUp 0.8s ease 0.6s forwards;
}

.hero-tags .tag {
    padding: 6px 18px;
    font-size: 14px;
    border: 1px solid var(--color-border);
    border-radius: 20px;
    color: var(--color-text-muted);
    background: rgba(30, 41, 59, 0.6);
    transition: all var(--transition-fast);
}

.hero-tags .tag:hover {
    border-color: var(--color-primary);
    color: var(--color-primary-light);
    background: rgba(37, 99, 235, 0.1);
}

.hero-cta {
    display: flex;
    justify-content: center;
    gap: 20px;
    opacity: 0;
    animation: fadeInUp 0.8s ease 0.8s forwards;
}

.hero-cta .btn {
    padding: 14px 32px;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    border: none;
}

.hero-cta .btn-primary {
    background: var(--color-primary);
    color: #fff;
}

.hero-cta .btn-primary:hover {
    background: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(37, 99, 235, 0.3);
}

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

.hero-cta .btn-outline:hover {
    border-color: var(--color-primary);
    color: var(--color-primary-light);
    transform: translateY(-2px);
}

.hero-scroll-indicator {
    position: absolute;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    opacity: 0.6;
    animation: bounce 2s infinite;
}

.hero-scroll-indicator span {
    font-size: 12px;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 2px;
}

.hero-scroll-indicator .mouse {
    width: 24px;
    height: 38px;
    border: 2px solid var(--color-text-muted);
    border-radius: 12px;
    position: relative;
}

.hero-scroll-indicator .mouse::after {
    content: '';
    position: absolute;
    top: 6px;
    left: 50%;
    transform: translateX(-50%);
    width: 3px;
    height: 8px;
    background: var(--color-text-muted);
    border-radius: 2px;
    animation: scrollWheel 1.5s infinite;
}

/* ============================================
   About Section 关于我
   ============================================ */
#about {
    background: var(--color-bg-secondary);
}

.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: start;
}

.about-info h3 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 20px;
    color: var(--color-text);
}

.about-info p {
    color: var(--color-text-secondary);
    margin-bottom: 20px;
    font-size: 16px;
    line-height: 1.8;
}

.about-details {
    list-style: none;
    display: grid;
    gap: 14px;
}

.about-details li {
    display: flex;
    align-items: center;
    gap: 12px;
    color: var(--color-text-muted);
    font-size: 15px;
}

.about-details .label {
    color: var(--color-text-secondary);
    font-weight: 600;
    min-width: 70px;
}

.about-details .divider {
    color: var(--color-border);
}

.about-details .value {
    color: var(--color-text);
}

.about-education {
    background: var(--color-bg-card);
    border-radius: 16px;
    padding: 30px;
    border: 1px solid var(--color-border);
}

.about-education h3 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.about-education h3 i {
    color: var(--color-primary-light);
}

.about-education .school {
    font-size: 18px;
    font-weight: 600;
    color: var(--color-text);
}

.about-education .degree {
    font-size: 14px;
    color: var(--color-accent);
    margin: 4px 0 16px;
}

.about-education .courses {
    font-size: 14px;
    color: var(--color-text-muted);
    line-height: 1.8;
}

.about-education .gpa-tag {
    display: inline-block;
    padding: 2px 10px;
    background: rgba(16, 185, 129, 0.15);
    color: var(--color-success);
    border-radius: 4px;
    font-size: 13px;
    font-weight: 600;
    margin-left: 6px;
}

/* ============================================
   Skills Section 技能
   ============================================ */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.skill-category {
    background: var(--color-bg-card);
    border-radius: 16px;
    padding: 30px;
    border: 1px solid var(--color-border);
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.skill-category:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
    border-color: rgba(37, 99, 235, 0.3);
}

.skill-category-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 20px;
}

.skill-category-icon {
    width: 44px;
    height: 44px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
}

.skill-category-icon.backend {
    background: rgba(37, 99, 235, 0.15);
    color: #3B82F6;
}

.skill-category-icon.ai {
    background: rgba(6, 182, 212, 0.15);
    color: #06B6D4;
}

.skill-category-icon.frontend {
    background: rgba(139, 92, 246, 0.15);
    color: #8B5CF6;
}

.skill-category-icon.devops {
    background: rgba(16, 185, 129, 0.15);
    color: #10B981;
}

.skill-category h3 {
    font-size: 18px;
    font-weight: 600;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.skill-tag {
    padding: 6px 14px;
    background: rgba(51, 65, 85, 0.5);
    border-radius: 6px;
    font-size: 13px;
    color: var(--color-text-secondary);
    transition: all var(--transition-fast);
    border: 1px solid transparent;
}

.skill-tag:hover {
    background: rgba(37, 99, 235, 0.15);
    border-color: rgba(37, 99, 235, 0.3);
    color: var(--color-primary-light);
}

/* 技能进度条 */
.skill-bars {
    margin-top: 50px;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.skill-bar-item {
    margin-bottom: 0;
}

.skill-bar-info {
    display: flex;
    justify-content: space-between;
    margin-bottom: 8px;
    font-size: 14px;
}

.skill-bar-name {
    color: var(--color-text-secondary);
    font-weight: 500;
}

.skill-bar-percent {
    color: var(--color-primary-light);
    font-weight: 600;
}

.skill-bar-track {
    height: 6px;
    background: var(--color-bg-light);
    border-radius: 3px;
    overflow: hidden;
}

.skill-bar-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    border-radius: 3px;
    width: 0;
    transition: width 1.5s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ============================================
   Experience Section 实习经历
   ============================================ */
#experience {
    background: var(--color-bg-secondary);
}

.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
    padding-left: 30px;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(180deg, var(--color-primary), var(--color-accent));
    border-radius: 1px;
}

.timeline-item {
    position: relative;
    padding-bottom: 50px;
}

.timeline-item:last-child {
    padding-bottom: 0;
}

.timeline-dot {
    position: absolute;
    left: -36px;
    top: 4px;
    width: 14px;
    height: 14px;
    background: var(--color-primary);
    border-radius: 50%;
    border: 3px solid var(--color-bg-secondary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.3);
}

.timeline-card {
    background: var(--color-bg-card);
    border-radius: 16px;
    padding: 28px;
    border: 1px solid var(--color-border);
    transition: transform var(--transition-normal);
}

.timeline-card:hover {
    transform: translateX(6px);
    border-color: rgba(37, 99, 235, 0.3);
}

.timeline-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
    margin-bottom: 16px;
}

.timeline-company {
    font-size: 20px;
    font-weight: 700;
    color: var(--color-text);
}

.timeline-date {
    font-size: 14px;
    color: var(--color-accent);
    background: rgba(6, 182, 212, 0.1);
    padding: 4px 14px;
    border-radius: 20px;
}

.timeline-role {
    font-size: 14px;
    color: var(--color-primary-light);
    font-weight: 600;
    margin-bottom: 16px;
}

.timeline-desc {
    color: var(--color-text-secondary);
    font-size: 15px;
    line-height: 1.8;
}

.timeline-desc p {
    margin-bottom: 12px;
}

.timeline-list {
    list-style: none;
    padding: 0;
}

.timeline-list li {
    position: relative;
    padding-left: 20px;
    margin-bottom: 10px;
    color: var(--color-text-muted);
    font-size: 14px;
    line-height: 1.7;
}

.timeline-list li::before {
    content: '▸';
    position: absolute;
    left: 0;
    top: 0;
    color: var(--color-primary-light);
    font-size: 12px;
}

/* ============================================
   Projects Section 项目经历
   ============================================ */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.project-card {
    background: var(--color-bg-card);
    border-radius: 16px;
    padding: 32px;
    border: 1px solid var(--color-border);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.project-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.project-card:hover::before {
    opacity: 1;
}

.project-card:hover {
    transform: translateY(-6px);
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.3);
    border-color: rgba(37, 99, 235, 0.3);
}

.project-card h3 {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 8px;
}

.project-subtitle {
    font-size: 14px;
    color: var(--color-accent);
    margin-bottom: 12px;
}

.project-tech-stack {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin-bottom: 16px;
}

.project-tech-tag {
    padding: 3px 10px;
    background: rgba(37, 99, 235, 0.1);
    color: var(--color-primary-light);
    border-radius: 4px;
    font-size: 12px;
    font-family: var(--font-mono);
}

.project-desc {
    color: var(--color-text-muted);
    font-size: 14px;
    line-height: 1.8;
    margin-bottom: 16px;
}

.project-achievements {
    list-style: none;
}

.project-achievements li {
    position: relative;
    padding-left: 18px;
    margin-bottom: 10px;
    color: var(--color-text-secondary);
    font-size: 14px;
    line-height: 1.7;
}

.project-achievements li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 9px;
    width: 6px;
    height: 6px;
    background: var(--color-success);
    border-radius: 50%;
}

.achievement-highlight {
    color: var(--color-success);
    font-weight: 600;
}

/* ============================================
   Campus Section 校园经历
   ============================================ */
#campus {
    background: var(--color-bg-secondary);
}

.campus-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.campus-card {
    background: var(--color-bg-card);
    border-radius: 16px;
    padding: 28px;
    border: 1px solid var(--color-border);
    transition: all var(--transition-normal);
}

.campus-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 30px rgba(0, 0, 0, 0.2);
    border-color: rgba(37, 99, 235, 0.3);
}

.campus-card .card-icon {
    font-size: 28px;
    margin-bottom: 16px;
}

.campus-card h4 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--color-text);
}

.campus-card p {
    font-size: 14px;
    color: var(--color-text-muted);
    line-height: 1.8;
}

/* ============================================
   Contact Section 联系方式
   ============================================ */
.contact-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
    max-width: 800px;
    margin: 0 auto;
}

.contact-card {
    background: var(--color-bg-card);
    border-radius: 16px;
    padding: 32px;
    border: 1px solid var(--color-border);
    text-align: center;
    transition: all var(--transition-normal);
    cursor: pointer;
}

.contact-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 30px rgba(0, 0, 0, 0.2);
    border-color: rgba(37, 99, 235, 0.3);
}

.contact-icon {
    width: 56px;
    height: 56px;
    border-radius: 50%;
    background: rgba(37, 99, 235, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 16px;
    font-size: 24px;
    color: var(--color-primary-light);
}

.contact-label {
    font-size: 14px;
    color: var(--color-text-muted);
    margin-bottom: 6px;
}

.contact-value {
    font-size: 16px;
    font-weight: 600;
    color: var(--color-text);
}

.contact-cta {
    text-align: center;
    margin-top: 40px;
}

.contact-cta .btn-primary {
    display: inline-block;
    padding: 16px 40px;
    background: var(--color-primary);
    color: #fff;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    transition: all var(--transition-fast);
}

.contact-cta .btn-primary:hover {
    background: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(37, 99, 235, 0.3);
}

/* ============================================
   Footer
   ============================================ */
.footer {
    text-align: center;
    padding: 32px 0;
    border-top: 1px solid var(--color-border);
    color: var(--color-text-muted);
    font-size: 14px;
}

/* ============================================
   Animations 动画
   ============================================ */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% { transform: translateX(-50%) translateY(0); }
    40% { transform: translateX(-50%) translateY(-10px); }
    60% { transform: translateX(-50%) translateY(-5px); }
}

@keyframes scrollWheel {
    0% { opacity: 1; transform: translateX(-50%) translateY(0); }
    100% { opacity: 0; transform: translateX(-50%) translateY(10px); }
}

/* Scroll-triggered animations */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease, transform 0.8s ease;
}

.reveal.visible {
    opacity: 1;
    transform: translateY(0);
}

.reveal-delay-1 { transition-delay: 0.1s; }
.reveal-delay-2 { transition-delay: 0.2s; }
.reveal-delay-3 { transition-delay: 0.3s; }
.reveal-delay-4 { transition-delay: 0.4s; }

/* ============================================
   Responsive 响应式 (电脑端为主)
   ============================================ */
@media (max-width: 1024px) {
    .hero-name {
        font-size: 44px;
    }
    .about-grid,
    .skills-grid,
    .skill-bars,
    .projects-grid,
    .campus-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav-links {
        gap: 16px;
    }
    .nav-links a {
        font-size: 13px;
    }
    .hero-name {
        font-size: 36px;
    }
    .hero-role {
        font-size: 18px;
    }
    .section {
        padding: 60px 0;
    }
    .contact-grid {
        grid-template-columns: 1fr;
    }
    .project-card {
        padding: 20px;
    }
}

@media (max-width: 480px) {
    .hero-name {
        font-size: 28px;
    }
    .hero-cta {
        flex-direction: column;
        align-items: center;
    }
    .hero-tags {
        gap: 8px;
    }
    .timeline-header {
        flex-direction: column;
        align-items: flex-start;
    }
}