/**
 * 向睿超（Richard Xiang）个人主页样式表
 * 设计理念：OpenAI 官方编辑式极简主义（Editorial Minimalism）
 * 特点：克制、严谨、层次鲜明、大留白、精密单色质感，坚决杜绝廉价“AI 塑料味”
 */

:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;

  /* 暗色主题（默认） */
  --bg-primary: #0a0a0a;
  --bg-surface: #121212;
  --bg-surface-hover: #181818;
  --bg-elevated: #1f1f1f;
  --header-bg: rgba(10, 10, 10, 0.85);

  --border: rgba(255, 255, 255, 0.12);
  --border-subtle: rgba(255, 255, 255, 0.06);
  --border-hover: rgba(255, 255, 255, 0.25);

  --text-primary: #f0f0f0;
  --text-secondary: #9a9a9a;
  --text-muted: #5e5e5e;

  --accent-text: #ffffff;
  --tag-bg: rgba(255, 255, 255, 0.05);
  --tag-border: rgba(255, 255, 255, 0.1);
  --tag-text: #b0b0b0;

  --btn-primary-bg: #f0f0f0;
  --btn-primary-text: #0a0a0a;
  --btn-primary-hover: #ffffff;

  --btn-secondary-bg: transparent;
  --btn-secondary-border: rgba(255, 255, 255, 0.16);
  --btn-secondary-text: #e0e0e0;
  --btn-secondary-hover: rgba(255, 255, 255, 0.08);

  --status-active: #10b981;

  --max-width: 980px;
  --container-padding: 24px;
}

[data-theme="light"] {
  --bg-primary: #ffffff;
  --bg-surface: #f9f9fa;
  --bg-surface-hover: #f1f1f3;
  --bg-elevated: #ffffff;
  --header-bg: rgba(255, 255, 255, 0.88);

  --border: rgba(0, 0, 0, 0.1);
  --border-subtle: rgba(0, 0, 0, 0.05);
  --border-hover: rgba(0, 0, 0, 0.22);

  --text-primary: #121212;
  --text-secondary: #5f5f65;
  --text-muted: #9c9ca3;

  --accent-text: #000000;
  --tag-bg: rgba(0, 0, 0, 0.04);
  --tag-border: rgba(0, 0, 0, 0.08);
  --tag-text: #4a4a50;

  --btn-primary-bg: #121212;
  --btn-primary-text: #ffffff;
  --btn-primary-hover: #000000;

  --btn-secondary-bg: transparent;
  --btn-secondary-border: rgba(0, 0, 0, 0.16);
  --btn-secondary-text: #1a1a1a;
  --btn-secondary-hover: rgba(0, 0, 0, 0.05);

  --status-active: #059669;
}

/* 基础重置 */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.65;
  transition: background-color 0.25s ease, color 0.25s ease;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* 布局容器 */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--container-padding);
  width: 100%;
}

/* 顶部导航 */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--header-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-subtle);
  transition: border-color 0.25s ease;
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  display: flex;
  align-items: baseline;
  gap: 10px;
  text-decoration: none;
  color: var(--text-primary);
}

.brand-name {
  font-size: 16px;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.brand-en {
  font-size: 13px;
  color: var(--text-secondary);
  font-weight: 400;
}

.status-dot {
  display: inline-block;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--status-active);
  margin-left: 2px;
  vertical-align: middle;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 28px;
  list-style: none;
}

.nav-link {
  font-size: 14px;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color 0.15s ease;
  font-weight: 400;
}

.nav-link:hover {
  color: var(--text-primary);
}

.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 5px 10px;
  border-radius: 6px;
  font-size: 12px;
  font-family: var(--font-mono);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all 0.2s ease;
}

.theme-toggle:hover {
  color: var(--text-primary);
  border-color: var(--border-hover);
  background-color: var(--tag-bg);
}

/* 移动端汉堡按钮 */
.mobile-toggle-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 20px;
  cursor: pointer;
}

/* 主内容区 */
main {
  flex: 1;
}

/* 统一 Section 排版 */
section {
  padding: 80px 0;
  border-bottom: 1px solid var(--border-subtle);
}

section:last-of-type {
  border-bottom: none;
}

.section-label {
  font-family: var(--font-mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.section-label::before {
  content: "";
  display: inline-block;
  width: 14px;
  height: 1px;
  background-color: var(--text-muted);
}

.section-title {
  font-size: 28px;
  font-weight: 500;
  letter-spacing: -0.02em;
  margin-bottom: 40px;
  color: var(--text-primary);
}

/* 1. HERO 导言区 */
.hero-section {
  padding: 100px 0 80px;
}

.hero-kicker {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.hero-title {
  font-size: 42px;
  font-weight: 500;
  line-height: 1.2;
  letter-spacing: -0.03em;
  color: var(--text-primary);
  margin-bottom: 24px;
  max-width: 820px;
}

.hero-lead {
  font-size: 18px;
  line-height: 1.7;
  color: var(--text-secondary);
  max-width: 760px;
  margin-bottom: 36px;
}

.hero-actions {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: 6px;
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
  transition: all 0.18s ease;
  cursor: pointer;
}

.btn-primary {
  background-color: var(--btn-primary-bg);
  color: var(--btn-primary-text);
  border: 1px solid transparent;
}

.btn-primary:hover {
  background-color: var(--btn-primary-hover);
  transform: translateY(-1px);
}

.btn-secondary {
  background-color: var(--btn-secondary-bg);
  color: var(--btn-secondary-text);
  border: 1px solid var(--btn-secondary-border);
}

.btn-secondary:hover {
  background-color: var(--btn-secondary-hover);
  border-color: var(--border-hover);
  color: var(--text-primary);
}

.arrow-icon {
  display: inline-block;
  transition: transform 0.15s ease;
}

a:hover .arrow-icon {
  transform: translate(2px, -2px);
}

/* 2. 精选工程列表（OpenAI Editorial List） */
.projects-list {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.project-item {
  background-color: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 32px;
  transition: border-color 0.2s ease, background-color 0.2s ease, transform 0.2s ease;
}

.project-item:hover {
  border-color: var(--border-hover);
  background-color: var(--bg-surface-hover);
  transform: translateY(-2px);
}

.project-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 12px;
  flex-wrap: wrap;
  gap: 10px;
}

.project-title {
  font-size: 22px;
  font-weight: 500;
  letter-spacing: -0.015em;
  color: var(--text-primary);
}

.project-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--text-muted);
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 16px;
}

.tag {
  font-family: var(--font-mono);
  font-size: 11px;
  padding: 3px 8px;
  border-radius: 4px;
  background-color: var(--tag-bg);
  border: 1px solid var(--tag-border);
  color: var(--tag-text);
}

.project-desc {
  font-size: 15px;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.project-links {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
  padding-top: 16px;
  border-top: 1px solid var(--border-subtle);
}

.project-link {
  font-size: 13px;
  color: var(--text-primary);
  text-decoration: none;
  font-weight: 500;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  transition: opacity 0.15s ease;
}

.project-link:hover {
  opacity: 0.75;
}

.project-link-badge {
  font-family: var(--font-mono);
  font-size: 10px;
  padding: 1px 6px;
  border-radius: 3px;
  background-color: var(--tag-bg);
  color: var(--text-secondary);
  margin-left: 4px;
}

/* 3. 研究关注（3列网格） */
.research-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.research-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 28px;
  display: flex;
  flex-direction: column;
}

.research-num {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 16px;
}

.research-card h3 {
  font-size: 17px;
  font-weight: 500;
  margin-bottom: 12px;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

.research-card p {
  font-size: 14px;
  line-height: 1.65;
  color: var(--text-secondary);
}

/* 4. 背景与技能（左右对齐网格） */
.background-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 36px;
}

.bg-col h3 {
  font-size: 16px;
  font-weight: 500;
  margin-bottom: 20px;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

.timeline-item {
  margin-bottom: 20px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border-subtle);
}

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

.timeline-role {
  font-size: 15px;
  font-weight: 500;
  color: var(--text-primary);
}

.timeline-org {
  font-size: 14px;
  color: var(--text-secondary);
  margin-top: 2px;
}

.timeline-time {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 4px;
}

.skills-category {
  margin-bottom: 16px;
}

.skills-category-title {
  font-family: var(--font-mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.skills-category-items {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* 5. 联系板块 */
.contact-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background-color: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 40px;
  flex-wrap: wrap;
  gap: 24px;
}

.contact-text h3 {
  font-size: 22px;
  font-weight: 500;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.contact-text p {
  font-size: 15px;
  color: var(--text-secondary);
  max-width: 500px;
}

.contact-links {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}

/* 6. 页脚合规与版权 */
.site-footer {
  padding: 48px 0;
  background-color: var(--bg-primary);
  border-top: 1px solid var(--border-subtle);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 20px;
  font-size: 13px;
  color: var(--text-muted);
}

.footer-compliance {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.footer-compliance a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color 0.15s ease;
}

.footer-compliance a:hover {
  color: var(--text-primary);
  text-decoration: underline;
}

.footer-tagline {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.04em;
}

/* 响应式适配 */
@media (max-width: 860px) {
  .research-grid {
    grid-template-columns: 1fr;
  }

  .background-grid {
    grid-template-columns: 1fr;
  }

  .hero-title {
    font-size: 34px;
  }
}

@media (max-width: 640px) {
  section {
    padding: 60px 0;
  }

  .hero-section {
    padding: 60px 0 40px;
  }

  .hero-title {
    font-size: 28px;
  }

  .hero-lead {
    font-size: 16px;
  }

  .nav-menu {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background-color: var(--bg-surface);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 20px;
    gap: 16px;
    align-items: flex-start;
  }

  .nav-menu.open {
    display: flex;
  }

  .mobile-toggle-btn {
    display: block;
  }

  .project-item {
    padding: 20px;
  }

  .contact-inner {
    padding: 24px;
    flex-direction: column;
    align-items: flex-start;
  }

  .footer-inner {
    flex-direction: column;
    align-items: flex-start;
  }
}