/* ============================================
   John Lei — Academic Personal Site
   Design: Minimal warmth with subtle character
   ============================================ */

/* --- Reset & Variables --- */
:root {
  --color-bg: #faf9f7;
  --color-surface: #ffffff;
  --color-text: #2d2d2d;
  --color-text-muted: #6b6b6b;
  --color-accent: #d4a373;
  --color-accent-light: #e8d5b7;
  --color-accent-dark: #b8854e;
  --color-border: #e8e6e3;
  --color-heading: #1a1a2e;
  --font-serif: 'Georgia', 'Noto Serif SC', serif;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans SC', sans-serif;
  --max-width: 820px;
  --nav-height: 64px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html { scroll-behavior: smooth; }

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

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* --- Typography --- */
h1, h2, h3, h4 {
  font-family: var(--font-serif);
  color: var(--color-heading);
  line-height: 1.3;
}

h2.section-title {
  font-size: 1.6rem;
  margin-bottom: 2rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

h2.section-title::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--color-border);
  margin-left: 1rem;
}

/* --- Navigation --- */
nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--nav-height);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background var(--transition), box-shadow var(--transition);
}

nav.scrolled {
  background: rgba(250, 249, 247, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 1px 0 var(--color-border);
}

.nav-inner {
  width: 100%;
  max-width: var(--max-width);
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-name {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  color: var(--color-heading);
  text-decoration: none;
  letter-spacing: 0.5px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--color-text-muted);
  font-size: 0.88rem;
  transition: color var(--transition);
  position: relative;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 1.5px;
  background: var(--color-accent);
  transition: width var(--transition);
}

.nav-links a:hover {
  color: var(--color-heading);
}

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

.lang-toggle {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 0.8rem;
  color: var(--color-text-muted);
  background: none;
  border: 1px solid var(--color-border);
  border-radius: 20px;
  padding: 3px 10px;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
}

.lang-toggle:hover {
  border-color: var(--color-accent);
  color: var(--color-accent-dark);
}

.lang-toggle .active {
  color: var(--color-accent-dark);
  font-weight: 600;
}

.lang-toggle .sep {
  color: var(--color-border);
}

/* --- Hero --- */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 100px 24px 80px;
  max-width: var(--max-width);
  margin: 0 auto;
  position: relative;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background:
    radial-gradient(ellipse at 20% 50%, rgba(212, 163, 115, 0.06) 0%, transparent 60%),
    radial-gradient(ellipse at 80% 50%, rgba(212, 163, 115, 0.04) 0%, transparent 60%);
  pointer-events: none;
}

.hero-name {
  font-size: 3.5rem;
  margin-bottom: 0.5rem;
  position: relative;
}

.hero-sub {
  font-family: var(--font-sans);
  font-size: 1.2rem;
  color: var(--color-accent-dark);
  font-weight: 400;
  margin-bottom: 1.5rem;
}

.hero-stripe {
  width: 60px;
  height: 2px;
  background: var(--color-accent);
  margin-bottom: 1.5rem;
}

.hero-desc {
  font-size: 1.05rem;
  color: var(--color-text-muted);
  max-width: 620px;
  line-height: 1.8;
  margin-bottom: 2rem;
}

.hero-links {
  display: flex;
  gap: 1.2rem;
  flex-wrap: wrap;
}

.hero-links a {
  text-decoration: none;
  color: var(--color-text-muted);
  font-size: 0.9rem;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: color var(--transition);
  padding: 4px 0;
}

.hero-links a:hover {
  color: var(--color-accent-dark);
}

.hero-links .btn-primary {
  background: var(--color-heading);
  color: white;
  padding: 8px 20px;
  border-radius: 24px;
  font-size: 0.88rem;
  transition: all var(--transition);
}

.hero-links .btn-primary:hover {
  background: var(--color-accent-dark);
  color: white;
}

/* --- Sections --- */
.section {
  padding: 80px 24px;
  max-width: var(--max-width);
  margin: 0 auto;
}

.section-alt {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}

/* --- Education --- */
.edu-item {
  display: flex;
  gap: 1.5rem;
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--color-border);
}

.edu-item:last-child { border-bottom: none; }

.edu-icon {
  flex-shrink: 0;
  width: 44px;
  height: 44px;
  background: var(--color-accent-light);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-accent-dark);
  font-size: 1.1rem;
}

.edu-body h3 {
  font-family: var(--font-sans);
  font-size: 1.05rem;
  margin-bottom: 0.3rem;
}

.edu-body .meta {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: 0.4rem;
}

.edu-body .detail {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* --- Research Cards --- */
.research-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}

.research-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 1.8rem;
  transition: all var(--transition);
  cursor: default;
}

.research-card:hover {
  border-color: var(--color-accent-light);
  box-shadow: 0 4px 20px rgba(0,0,0,0.06);
  transform: translateY(-2px);
}

.research-card .tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--color-accent-dark);
  background: var(--color-accent-light);
  padding: 2px 10px;
  border-radius: 12px;
  margin-bottom: 0.8rem;
}

.research-card h3 {
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
}

.research-card .date {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin-bottom: 0.8rem;
}

.research-card .role {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-accent-dark);
  margin-bottom: 0.6rem;
}

.research-card p {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.7;
}

.research-card .methods {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 1rem;
}

.research-card .methods span {
  font-size: 0.75rem;
  background: var(--color-bg);
  padding: 2px 10px;
  border-radius: 10px;
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
}

/* --- Experience --- */
.exp-item {
  display: flex;
  gap: 1.5rem;
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--color-border);
}

.exp-item:last-child { border-bottom: none; }

.exp-icon {
  flex-shrink: 0;
  width: 44px;
  height: 44px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
}

.exp-icon.workshop { background: #e3f0fa; color: #2c7a9e; }
.exp-icon.contest { background: #f0e6f6; color: #7b5e9b; }
.exp-icon.dev { background: #e6f5e6; color: #3a8a5e; }

.exp-body h3 {
  font-family: var(--font-sans);
  font-size: 1rem;
  margin-bottom: 0.2rem;
}

.exp-body .meta {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin-bottom: 0.5rem;
}

.exp-body p {
  font-size: 0.88rem;
  color: var(--color-text-muted);
  line-height: 1.7;
}

/* --- Skills --- */
.skills-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.skill-cat {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 1.3rem 1.5rem;
}

.skill-cat h4 {
  font-family: var(--font-sans);
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--color-accent-dark);
  margin-bottom: 0.8rem;
}

.skill-cat .tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.skill-cat .tags span {
  font-size: 0.8rem;
  background: var(--color-bg);
  padding: 3px 10px;
  border-radius: 8px;
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

/* --- Contact --- */
.contact-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 1.2rem;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 0.8rem 1.2rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  text-decoration: none;
  color: var(--color-text);
  font-size: 0.9rem;
  transition: all var(--transition);
}

.contact-item:hover {
  border-color: var(--color-accent);
  transform: translateY(-2px);
  box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

.contact-item .icon {
  color: var(--color-accent-dark);
  font-size: 1.1rem;
}

/* --- Footer --- */
footer {
  text-align: center;
  padding: 3rem 24px;
  color: var(--color-text-muted);
  font-size: 0.8rem;
  border-top: 1px solid var(--color-border);
}

/* --- Scroll reveal --- */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

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

/* Bilingual: hidden by default, toggled by JS */
.zh, .en { display: none; }

/* --- Project Cards (grid) --- */
.proj-grid {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.proj-card {
  display: flex;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  overflow: hidden;
  transition: all var(--transition);
}
.proj-card:hover {
  border-color: var(--color-accent-light);
  box-shadow: 0 4px 16px rgba(0,0,0,0.06);
}

.proj-cover {
  flex-shrink: 0;
  width: 200px;
  min-height: 150px;
  background: var(--color-bg);
}
.proj-cover img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

.proj-body {
  flex: 1;
  padding: 1.2rem 1.3rem;
  display: flex;
  flex-direction: column;
}
.proj-body h3 {
  font-family: var(--font-sans);
  font-size: 1.05rem;
  margin-bottom: 0.3rem;
  font-weight: 600;
}
.proj-body p {
  font-size: 0.88rem;
  color: var(--color-text-muted);
  line-height: 1.7;
  flex: 1;
}

.proj-foot {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 0.8rem;
  margin-top: 0.6rem;
  padding-top: 0.6rem;
  border-top: 1px solid var(--color-border);
}
.proj-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem;
}
.proj-tags span {
  font-size: 0.7rem;
  padding: 2px 8px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  color: var(--color-text-muted);
}
.proj-links {
  display: flex;
  gap: 0.6rem;
  margin-left: auto;
}
.proj-links a {
  font-size: 0.78rem;
  color: var(--color-accent-dark);
  text-decoration: none;
  white-space: nowrap;
}
.proj-links a:hover {
  text-decoration: underline;
}
.proj-status {
  font-size: 0.72rem;
  color: var(--color-accent-dark);
  font-weight: 500;
  white-space: nowrap;
}

/* --- Contact chip --- */
.contact-chip {
  display: inline-block;
  padding: 0.7rem 1.4rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  text-decoration: none;
  color: var(--color-text);
  font-size: 0.92rem;
  transition: all var(--transition);
}
.contact-chip:hover {
  border-color: var(--color-accent);
  transform: translateY(-2px);
  box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

/* --- Simple project cards --- */
.project-simple {
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--color-border);
}
.project-simple:last-child { border-bottom: none; }
.project-simple h3 {
  font-family: var(--font-sans);
  font-size: 1.15rem;
  margin-bottom: 0.3rem;
}
.project-simple p {
  font-size: 0.92rem;
  color: var(--color-text-muted);
  line-height: 1.7;
  margin-top: 0.4rem;
}

/* --- Responsive --- */
@media (max-width: 700px) {
  .hero { min-height: 90vh; min-height: 90dvh; padding: 80px 20px 60px; }
  .hero-name { font-size: 2.4rem; }
  .hero-sub { font-size: 1rem; }
  .section { padding: 60px 20px; }
  .nav-links { gap: 1rem; }
  .nav-links a { font-size: 0.82rem; }
  .skills-grid { grid-template-columns: 1fr; }
  .hero-links .btn-primary { padding: 6px 16px; font-size: 0.82rem; }
  .edu-item, .exp-item { gap: 1rem; }
  .proj-card { flex-direction: column; }
  .proj-cover { width: 100%; height: 180px; }
}

@media (max-width: 480px) {
  .hero-name { font-size: 1.8rem; }
  .nav-links { gap: 0.6rem; }
  .nav-links a { font-size: 0.78rem; }
  .lang-toggle { font-size: 0.72rem; padding: 2px 8px; }
  .proj-cover { height: 160px; }
  .proj-body { padding: 1rem; }
}