/* ========================================
   Jiaxiang Tang — Personal Website Styles
   ======================================== */

:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-accent: #0ea5e9;
  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-border: #e2e8f0;
  --color-nav-bg: rgba(255, 255, 255, 0.92);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.10);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.12);
  --radius: 12px;
  --radius-sm: 8px;
  --nav-height: 64px;
  --max-width: 900px;
}

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

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--nav-height) + 16px); }

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--color-primary); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--color-primary-dark); }

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

/* ---- Layout ---- */

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

/* ---- Navbar ---- */

.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-height);
  background: var(--color-nav-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  z-index: 100;
}

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

.nav-brand {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--color-text);
  letter-spacing: -0.01em;
  white-space: nowrap;
}
.nav-brand:hover { color: var(--color-primary); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}

.nav-links a {
  color: var(--color-text-muted);
  font-size: 0.9rem;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: 6px;
  white-space: nowrap;
  transition: background 0.15s, color 0.15s;
}
.nav-links a:hover { color: var(--color-primary); background: #eff6ff; }

.btn-cv {
  background: var(--color-primary) !important;
  color: #fff !important;
  border-radius: 6px;
  padding: 6px 14px !important;
  font-weight: 600 !important;
}
.btn-cv:hover { background: var(--color-primary-dark) !important; }

/* ---- Hero ---- */

.hero {
  padding: calc(var(--nav-height) + 64px) 0 64px;
}

.hero-inner {
  display: flex;
  gap: 48px;
  align-items: flex-start;
}

.hero-photo {
  flex-shrink: 0;
}

.hero-photo img {
  width: 160px;
  height: 196px;
  object-fit: cover;
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
}

.hero-text { flex: 1; }

.hero-text h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 4px;
  color: var(--color-text);
}

.chinese {
  color: var(--color-text-muted);
  font-weight: 400;
  font-size: 0.85em;
}

.hero-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: 2px;
}

.hero-affil {
  font-size: 0.92rem;
  color: var(--color-text-muted);
  margin-bottom: 16px;
}

.hero-bio {
  font-size: 0.95rem;
  color: var(--color-text);
  line-height: 1.75;
  margin-bottom: 20px;
}

.hero-links {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.link-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  color: var(--color-text) !important;
  font-size: 0.85rem;
  font-weight: 500;
  padding: 7px 14px;
  border-radius: 8px;
  transition: border-color 0.2s, box-shadow 0.2s, background 0.2s;
}
.link-badge:hover {
  border-color: var(--color-primary);
  background: #eff6ff;
  color: var(--color-primary) !important;
  box-shadow: var(--shadow-sm);
}

.link-badge-primary {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff !important;
}

.link-badge-primary:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  color: #fff !important;
}

/* ---- Sections ---- */

.section {
  padding: 72px 0;
}

.section-alt {
  background: var(--color-bg-alt);
}

.section-title {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 6px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--color-border);
  margin-bottom: 32px;
  color: var(--color-text);
}

.subsection-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--color-text);
  margin-top: 40px;
  margin-bottom: 16px;
}

.section-note {
  font-size: 0.88rem;
  color: var(--color-text-muted);
  margin-bottom: 24px;
  margin-top: -16px;
}

.section-subtext {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  margin-top: -20px;
  margin-bottom: 28px;
  line-height: 1.65;
}

/* ---- Home tracker callout ---- */

.home-tracker-callout {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 28px;
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-primary);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: var(--color-bg);
  padding: 24px 26px;
  box-shadow: var(--shadow-sm);
}

.home-tracker-label {
  font-size: 0.76rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: 6px;
}

.home-tracker-callout h2 {
  font-size: 1.24rem;
  line-height: 1.35;
  letter-spacing: -0.02em;
  margin-bottom: 8px;
}

.home-tracker-callout p {
  max-width: 650px;
  font-size: 0.92rem;
  color: var(--color-text-muted);
  line-height: 1.65;
}

.home-tracker-button {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 38px;
  padding: 8px 16px;
  border-radius: 7px;
  background: var(--color-primary);
  color: #fff !important;
  font-size: 0.86rem;
  font-weight: 700;
}

.home-tracker-button:hover {
  background: var(--color-primary-dark);
}

/* ---- Research Interest Cards ---- */

.interest-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 16px;
}

.interest-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px 20px;
  transition: box-shadow 0.2s, transform 0.2s;
}

.interest-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.interest-icon {
  font-size: 1.8rem;
  margin-bottom: 12px;
}

.interest-card h3 {
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--color-text);
}

.interest-card p {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ---- Current Work ---- */

.work-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.work-list li {
  padding-left: 20px;
  position: relative;
  font-size: 0.95rem;
  color: var(--color-text);
}

.work-list li::before {
  content: "→";
  position: absolute;
  left: 0;
  color: var(--color-primary);
  font-weight: 600;
}

/* ---- Publications ---- */

.pub-list {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.pub-item {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-primary);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 18px 20px;
  transition: box-shadow 0.2s;
}
.pub-item:hover { box-shadow: var(--shadow-sm); }

.pub-venue {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-primary);
  margin-bottom: 6px;
}

.pub-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 4px;
  line-height: 1.5;
}

.pub-authors {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: 4px;
}

.pub-links {
  display: flex;
  gap: 10px;
  margin-top: 10px;
}

.pub-link {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-primary);
  background: #eff6ff;
  padding: 3px 10px;
  border-radius: 4px;
  transition: background 0.15s;
}
.pub-link:hover { background: #dbeafe; }

/* ---- Education Timeline ---- */

.timeline {
  display: flex;
  flex-direction: column;
  gap: 0;
  border-left: 2px solid var(--color-border);
  margin-left: 8px;
  padding-left: 0;
}

.timeline-item {
  display: flex;
  gap: 20px;
  position: relative;
  padding-bottom: 32px;
}

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

.timeline-dot {
  flex-shrink: 0;
  width: 12px;
  height: 12px;
  background: var(--color-primary);
  border: 2px solid var(--color-bg);
  border-radius: 50%;
  margin-top: 4px;
  margin-left: -7px;
  box-shadow: 0 0 0 2px var(--color-primary);
}

.timeline-body { flex: 1; }

.timeline-period {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--color-primary);
  font-family: var(--font-mono);
  margin-bottom: 2px;
}

.timeline-degree {
  font-size: 0.98rem;
  font-weight: 600;
  color: var(--color-text);
}

.timeline-school {
  font-size: 0.88rem;
  color: var(--color-text-muted);
}

.award-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.award-list li {
  padding-left: 20px;
  position: relative;
  font-size: 0.92rem;
}

.award-list li::before {
  content: "🏆";
  position: absolute;
  left: 0;
  font-size: 0.85rem;
}

/* ---- Publication draft variant ---- */
.pub-item-draft {
  opacity: 0.65;
  border-left-color: var(--color-text-muted);
}

/* ---- Timeline extras ---- */
.timeline-detail {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin-top: 2px;
  line-height: 1.5;
}
.gpa {
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
}

/* ---- Skills grid ---- */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
}
.skill-group {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
}
.skill-label {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-primary);
  margin-bottom: 10px;
}
.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.skill-tags span {
  font-size: 0.8rem;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 3px 9px;
  color: var(--color-text);
  font-family: var(--font-mono);
}

/* ---- Footer ---- */

.footer {
  background: var(--color-bg-alt);
  border-top: 1px solid var(--color-border);
  padding: 32px 0;
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.footer a { color: var(--color-text-muted); }
.footer a:hover { color: var(--color-primary); }

/* ---- Interview prep tracker ---- */

.prep-page {
  background: var(--color-bg);
}

.prep-hero {
  padding: calc(var(--nav-height) + 56px) 0 56px;
  border-bottom: 1px solid var(--color-border);
}

.prep-hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 280px;
  gap: 32px;
  align-items: stretch;
}

.prep-kicker {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: 10px;
}

.prep-hero h1 {
  font-size: 2.1rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.18;
  margin-bottom: 14px;
}

.prep-lede {
  max-width: 660px;
  color: var(--color-text-muted);
  line-height: 1.75;
  font-size: 0.98rem;
}

.prep-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 24px;
}

.prep-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 38px;
  padding: 8px 16px;
  border-radius: 7px;
  background: var(--color-primary);
  color: #fff !important;
  font-size: 0.86rem;
  font-weight: 700;
  border: 1px solid var(--color-primary);
}

.prep-button:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
}

.prep-button-secondary {
  background: var(--color-bg);
  color: var(--color-primary) !important;
}

.prep-button-secondary:hover {
  background: #eff6ff;
  color: var(--color-primary-dark) !important;
}

.prep-summary {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 20px;
  background: var(--color-bg-alt);
  box-shadow: var(--shadow-sm);
}

.prep-summary-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: 12px;
}

.prep-summary-row strong {
  color: var(--color-text);
  font-family: var(--font-mono);
}

.prep-meter {
  height: 9px;
  border-radius: 999px;
  background: #e2e8f0;
  overflow: hidden;
}

.prep-meter span {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), #059669);
  transition: width 0.2s ease;
}

.prep-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin-top: 18px;
}

.prep-stats div {
  border: 1px solid var(--color-border);
  border-radius: 7px;
  background: var(--color-bg);
  padding: 10px 8px;
}

.prep-stats strong,
.prep-stats span {
  display: block;
  text-align: center;
}

.prep-stats strong {
  font-family: var(--font-mono);
  font-size: 1rem;
  color: var(--color-text);
}

.prep-stats span {
  font-size: 0.72rem;
  color: var(--color-text-muted);
}

.prep-reset {
  width: 100%;
  margin-top: 16px;
  border: 1px solid var(--color-border);
  border-radius: 7px;
  background: var(--color-bg);
  color: var(--color-text-muted);
  font: inherit;
  font-size: 0.82rem;
  font-weight: 600;
  padding: 8px 12px;
  cursor: pointer;
}

.prep-reset:hover {
  border-color: #f59e0b;
  color: #92400e;
  background: #fffbeb;
}

.prep-section {
  padding: 56px 0;
}

.prep-section-alt {
  background: var(--color-bg-alt);
}

.prep-week-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: -14px;
  margin-bottom: 24px;
}

.prep-week-nav a {
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: var(--color-bg);
  color: var(--color-text-muted);
  font-size: 0.82rem;
  font-weight: 700;
  padding: 5px 13px;
}

.prep-week-nav a:hover {
  border-color: var(--color-primary);
  background: #eff6ff;
  color: var(--color-primary);
}

.prep-principles {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}

.prep-principles div,
.prep-routine-card {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  padding: 18px;
}

.prep-principles h3,
.prep-routine-card h3 {
  font-size: 0.94rem;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--color-text);
}

.prep-principles p {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.65;
}

.prep-week {
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-primary);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: var(--color-bg);
  padding: 24px;
  margin-bottom: 20px;
  box-shadow: var(--shadow-sm);
}

.prep-week.is-complete {
  border-left-color: #059669;
}

.prep-week-header {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: flex-start;
  margin-bottom: 10px;
}

.prep-week-label {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--color-primary);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 4px;
}

.prep-week h3 {
  font-size: 1.08rem;
  line-height: 1.35;
  letter-spacing: -0.01em;
}

.prep-week-progress {
  flex-shrink: 0;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: var(--color-bg-alt);
  color: var(--color-text-muted);
  font-size: 0.76rem;
  font-weight: 700;
  font-family: var(--font-mono);
  padding: 4px 10px;
}

.prep-week-goal {
  color: var(--color-text-muted);
  font-size: 0.88rem;
  line-height: 1.6;
  margin-bottom: 18px;
}

.prep-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 22px;
}

.prep-columns h4 {
  color: var(--color-text);
  font-size: 0.82rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 10px;
}

.prep-task-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 9px;
}

.prep-task-list li {
  color: var(--color-text);
  font-size: 0.88rem;
  line-height: 1.55;
}

.prep-task-list label {
  display: grid;
  grid-template-columns: 18px minmax(0, 1fr);
  gap: 9px;
  align-items: start;
  cursor: pointer;
}

.prep-task-list input[type="checkbox"] {
  width: 16px;
  height: 16px;
  margin-top: 4px;
  accent-color: var(--color-primary);
}

.prep-task-list label:has(input:checked) {
  color: var(--color-text-muted);
  text-decoration: line-through;
  text-decoration-thickness: 1px;
}

.prep-routine-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}

/* ---- Responsive ---- */

@media (max-width: 640px) {
  :root { --nav-height: 112px; }
  .nav-inner {
    flex-direction: column;
    align-items: flex-start;
    justify-content: center;
    gap: 8px;
    padding-top: 10px;
    padding-bottom: 10px;
  }
  .nav-links {
    width: 100%;
    flex-wrap: nowrap;
    overflow-x: auto;
    padding-bottom: 3px;
    scrollbar-width: none;
  }
  .nav-links::-webkit-scrollbar { display: none; }
  .hero-inner { flex-direction: column; gap: 24px; }
  .hero-photo img { width: 120px; height: 147px; }
  .hero-text h1 { font-size: 1.5rem; }
  .interest-grid { grid-template-columns: 1fr 1fr; }
  .nav-links a { padding: 5px 8px; }
  .nav-links a { flex: 0 0 auto; }
  .home-tracker-callout {
    flex-direction: column;
    align-items: flex-start;
    padding: 20px;
  }
  .home-tracker-button { width: 100%; }
  .prep-hero-grid,
  .prep-principles,
  .prep-columns,
  .prep-routine-grid {
    grid-template-columns: 1fr;
  }
  .prep-hero h1 { font-size: 1.55rem; }
  .prep-week { padding: 20px; }
  .prep-week-header { flex-direction: column; }
}

@media (max-width: 400px) {
  .interest-grid { grid-template-columns: 1fr; }
}