/* Haocheng Li — portfolio. Plain CSS, no build step. */

:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --surface-2: #eef1f5;
  --text: #14171c;
  --text-2: #4a525e;
  --text-3: #7a8390;
  --line: #e2e6ec;
  --accent: #2a62d8;
  --accent-soft: #e6eefc;
  --shadow: 0 1px 2px rgba(20, 23, 28, .04), 0 8px 24px rgba(20, 23, 28, .06);
  --radius: 14px;
  --radius-lg: 20px;
  --shell: 1120px;
  --sans: "Inter", "Segoe UI", system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Code", Consolas, monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e1013;
    --surface: #16191e;
    --surface-2: #1d2128;
    --text: #eef1f5;
    --text-2: #b3bac5;
    --text-3: #808996;
    --line: #262b33;
    --accent: #7aa5ff;
    --accent-soft: #1b2638;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 8px 24px rgba(0, 0, 0, .25);
    color-scheme: dark;
  }
}

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

html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.65 var(--sans);
  -webkit-font-smoothing: antialiased;
}

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

a { color: inherit; text-decoration: none; }

h1, h2, h3 { margin: 0; line-height: 1.15; letter-spacing: -0.02em; font-weight: 700; }

p { margin: 0; }

.shell { width: min(var(--shell), 100% - 32px); margin-inline: auto; }

/* ---------- Nav ---------- */

.nav {
  position: sticky;
  top: 0;
  z-index: 10;
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: saturate(1.4) blur(12px);
  -webkit-backdrop-filter: saturate(1.4) blur(12px);
  border-bottom: 1px solid transparent;
  transition: border-color .2s;
}
.nav.is-scrolled { border-bottom-color: var(--line); }
.nav .shell { display: flex; align-items: center; justify-content: space-between; height: 64px; }

.wordmark { display: flex; align-items: center; gap: 10px; font-weight: 650; letter-spacing: -0.01em; }
.mark {
  display: grid; place-items: center;
  width: 32px; height: 32px; border-radius: 9px;
  background: var(--text); color: var(--bg);
  font-size: 13px; font-weight: 700; letter-spacing: 0;
}

.navLinks { display: flex; gap: 4px; }
.navLinks a {
  padding: 6px 12px; border-radius: 8px;
  color: var(--text-2); font-size: 15px;
  transition: background .15s, color .15s;
}
.navLinks a:hover { background: var(--surface-2); color: var(--text); }

.navRight { display: flex; align-items: center; gap: 8px; }

/* Language menu: a native <details> dropdown, no JS needed. */
.lang { position: relative; }
.lang summary {
  list-style: none; cursor: pointer;
  display: flex; align-items: center; gap: 6px;
  height: 34px; padding: 0 12px; border-radius: 8px;
  border: 1px solid var(--line); background: var(--surface);
  color: var(--text-2); font-size: 14px; font-weight: 600;
}
.lang summary::-webkit-details-marker { display: none; }
.lang summary::after { content: "▾"; font-size: 11px; color: var(--text-3); }
.lang summary:hover { color: var(--text); border-color: var(--text-3); }
.lang ul {
  position: absolute; right: 0; top: calc(100% + 6px);
  min-width: 140px; margin: 0; padding: 6px; list-style: none;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: 12px; box-shadow: var(--shadow);
}
.lang li a { display: block; padding: 7px 10px; border-radius: 8px; font-size: 14px; color: var(--text-2); }
.lang li a:hover { background: var(--surface-2); color: var(--text); }
.lang li a[aria-current="true"] { color: var(--accent); font-weight: 600; }

/* Per-language font stacks so CJK text uses the right glyphs. */
:lang(zh) body, body:lang(zh) { font-family: "Inter", "Segoe UI", system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif; }
:lang(ja) body, body:lang(ja) { font-family: "Inter", "Segoe UI", system-ui, -apple-system, "Hiragino Sans", "Yu Gothic UI", "Meiryo", "Noto Sans JP", sans-serif; }
:lang(ko) body, body:lang(ko) { font-family: "Inter", "Segoe UI", system-ui, -apple-system, "Apple SD Gothic Neo", "Malgun Gothic", "Noto Sans KR", sans-serif; }
:lang(zh) h1, :lang(ja) h1, :lang(ko) h1, :lang(zh) h2, :lang(ja) h2, :lang(ko) h2 { letter-spacing: -0.01em; }
:lang(zh) .bio, :lang(ja) .bio, :lang(ko) .bio, :lang(zh) .prose p, :lang(ja) .prose p, :lang(ko) .prose p { line-height: 1.8; }

/* ---------- Shared bits ---------- */

.eyebrow {
  color: var(--accent);
  font: 600 13px/1.4 var(--mono);
  letter-spacing: .06em;
  text-transform: uppercase;
}

.sectionHead { display: flex; align-items: end; justify-content: space-between; gap: 24px; margin-bottom: 32px; }
.sectionHead h2 { font-size: clamp(28px, 4vw, 40px); margin-top: 8px; }
.sectionHead .count { color: var(--text-3); font: 14px var(--mono); white-space: nowrap; }

section { padding: 88px 0; }

.btn {
  display: inline-flex; align-items: center; gap: 8px;
  height: 44px; padding: 0 20px; border-radius: 999px;
  font-weight: 600; font-size: 15px;
  border: 1px solid var(--line);
  background: var(--surface);
  transition: transform .15s, background .15s, border-color .15s;
}
.btn:hover { transform: translateY(-1px); border-color: var(--text-3); }
.btn.primary { background: var(--text); color: var(--bg); border-color: var(--text); }
.btn.primary:hover { background: var(--accent); border-color: var(--accent); color: #fff; }

.link {
  display: inline-flex; align-items: center; gap: 6px;
  color: var(--accent); font-weight: 600; font-size: 15px;
}
.link:hover { text-decoration: underline; text-underline-offset: 3px; }

.tags { display: flex; flex-wrap: wrap; gap: 6px; padding: 0; margin: 0; list-style: none; }
.tags li {
  padding: 3px 10px; border-radius: 999px;
  background: var(--surface-2); color: var(--text-2);
  font-size: 13px;
}

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

.hero { padding: 96px 0 64px; }
.hero h1 { font-size: clamp(44px, 8vw, 88px); letter-spacing: -0.035em; line-height: 1.02; }
.hero h1 span { color: var(--text-3); font-weight: 600; }
.hero .role { margin-top: 20px; font-size: clamp(20px, 2.6vw, 26px); color: var(--text-2); font-weight: 500; letter-spacing: -0.01em; }
.hero .bio { margin-top: 24px; max-width: 680px; color: var(--text-2); font-size: 17px; }
.hero .bio + .bio { margin-top: 12px; }
.heroActions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 36px; }

.facts { display: flex; flex-wrap: wrap; gap: 8px 28px; margin-top: 48px; padding-top: 28px; border-top: 1px solid var(--line); }
.facts div { display: flex; flex-direction: column; }
.facts dt { color: var(--text-3); font: 12px var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.facts dd { margin: 2px 0 0; font-weight: 600; font-size: 15px; }

/* ---------- Project cards ---------- */

.projects { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }

.card {
  display: flex; flex-direction: column;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: transform .2s, box-shadow .2s;
}
.card:hover { transform: translateY(-3px); }

.cardMedia { position: relative; aspect-ratio: 16 / 10; background: var(--surface-2); overflow: hidden; }
.cardMedia img, .cardMedia video { width: 100%; height: 100%; object-fit: cover; }
.cardMedia .badge {
  position: absolute; top: 12px; left: 12px;
  padding: 4px 10px; border-radius: 999px;
  background: rgba(10, 12, 16, .62); color: #fff;
  font: 600 12px var(--mono); letter-spacing: .04em;
  backdrop-filter: blur(6px);
}

.cardBody { display: flex; flex-direction: column; gap: 12px; padding: 24px; flex: 1; }
.cardBody .context { color: var(--text-3); font: 12px var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.cardBody h3 { font-size: 22px; }
.cardBody .summary { color: var(--text-2); }
.cardBody ul.points { margin: 0; padding-left: 18px; color: var(--text-2); font-size: 15px; }
.cardBody ul.points li + li { margin-top: 4px; }
.cardLinks { display: flex; flex-wrap: wrap; gap: 8px 20px; margin-top: auto; padding-top: 8px; }

/* The featured project spans the full row, media beside text. */
.card.featured { grid-column: 1 / -1; flex-direction: row; }
.card.featured .cardMedia { flex: 1.25; aspect-ratio: auto; min-height: 380px; }
.card.featured .cardBody { flex: 1; padding: 36px; justify-content: center; }
.card.featured h3 { font-size: 32px; }

/* Virtual Pet has no footage: a simple illustrated tile. */
.petTile {
  width: 100%; height: 100%;
  display: grid; place-items: center;
  background:
    radial-gradient(circle at 30% 30%, #ffd8a8 0, transparent 45%),
    radial-gradient(circle at 75% 70%, #b8d8ff 0, transparent 50%),
    linear-gradient(135deg, #fff4e6, #e7f0ff);
}
.petTile .pet {
  position: relative; width: 120px; height: 100px;
  background: #fff; border-radius: 60px 60px 48px 48px;
  box-shadow: 0 10px 30px rgba(42, 98, 216, .18);
}
.petTile .pet::before, .petTile .pet::after {
  content: ""; position: absolute; top: 40px; width: 10px; height: 14px;
  border-radius: 50%; background: #1d2330;
}
.petTile .pet::before { left: 38px; }
.petTile .pet::after { right: 38px; }
.petTile .timer {
  position: absolute; bottom: 18px; right: 18px;
  padding: 4px 10px; border-radius: 999px;
  background: rgba(255, 255, 255, .8); color: #1d2330;
  font: 600 13px var(--mono);
}

/* ---------- Systems ---------- */

.systems { background: var(--surface); border-block: 1px solid var(--line); }
.grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.tile {
  display: flex; flex-direction: column; gap: 10px;
  padding: 24px; border-radius: var(--radius);
  background: var(--bg); border: 1px solid var(--line);
}
.tile .area { color: var(--accent); font: 600 12px var(--mono); letter-spacing: .06em; text-transform: uppercase; }
.tile h3 { font-size: 20px; }
.tile p { color: var(--text-2); font-size: 15px; }
.tile .result { margin-top: auto; padding-top: 8px; font-weight: 600; }
.tile .tools { color: var(--text-3); font: 13px var(--mono); }

/* ---------- Experience ---------- */

.expGrid { display: grid; grid-template-columns: 1.5fr 1fr; gap: 48px; }

.timeline { display: flex; flex-direction: column; }
.timeline article {
  display: grid; grid-template-columns: 72px 1fr; gap: 16px;
  padding: 20px 0; border-top: 1px solid var(--line);
}
.timeline article:last-child { border-bottom: 1px solid var(--line); }
.timeline .year { color: var(--text-3); font: 14px var(--mono); padding-top: 2px; }
.timeline .where { color: var(--text-3); font-size: 14px; }
.timeline h3 { font-size: 18px; margin: 2px 0 6px; }
.timeline p { color: var(--text-2); font-size: 15px; }

.edu { display: flex; flex-direction: column; gap: 16px; }
.edu .school {
  padding: 20px; border-radius: var(--radius);
  background: var(--surface); border: 1px solid var(--line);
}
.edu .school span { color: var(--text-3); font: 13px var(--mono); }
.edu .school h3 { font-size: 17px; margin: 4px 0; }
.edu .school p { color: var(--text-2); font-size: 15px; }

.skills { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 16px; margin-top: 56px; }
.skills div { padding-top: 14px; border-top: 2px solid var(--text); }
.skills span { font: 600 12px var(--mono); letter-spacing: .06em; color: var(--text-3); }
.skills p { margin-top: 6px; font-size: 15px; }

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

.footer { padding: 40px 0 56px; border-top: 1px solid var(--line); color: var(--text-3); font-size: 14px; }
.footer .shell { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; }
.footer a:hover { color: var(--text); }

/* ---------- Project detail pages ---------- */

.detailHero { padding: 72px 0 40px; }
.detailHero h1 { font-size: clamp(40px, 7vw, 72px); letter-spacing: -0.035em; margin-top: 12px; }
.detailHero .lede { margin-top: 20px; max-width: 680px; font-size: 19px; color: var(--text-2); }
.detailHero .heroActions { margin-top: 28px; }

.frame {
  border-radius: var(--radius-lg); overflow: hidden;
  background: #000; border: 1px solid var(--line);
  box-shadow: var(--shadow);
}
.frame video, .frame img { width: 100%; }
.caption { margin-top: 12px; color: var(--text-3); font-size: 14px; }

.split { display: grid; grid-template-columns: 1fr 1.3fr; gap: 56px; }
.split h2 { font-size: clamp(28px, 4vw, 40px); margin-top: 8px; }
.prose p { color: var(--text-2); font-size: 17px; }
.prose p + p { margin-top: 16px; }

.specs { display: grid; grid-template-columns: repeat(2, 1fr); gap: 16px; margin: 32px 0 0; }
.specs div { padding-top: 12px; border-top: 1px solid var(--line); }
.specs dt { color: var(--text-3); font: 12px var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.specs dd { margin: 4px 0 0; font-weight: 600; }

.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.features article {
  padding: 24px; border-radius: var(--radius);
  background: var(--surface); border: 1px solid var(--line);
}
.features .num { color: var(--accent); font: 600 13px var(--mono); }
.features h3 { font-size: 18px; margin: 10px 0 8px; }
.features p { color: var(--text-2); font-size: 15px; }

.gallery { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }
.gallery figure { margin: 0; }
.gallery figcaption { margin-top: 12px; }
.gallery figcaption strong { display: block; font-size: 17px; }
.gallery figcaption span { color: var(--text-2); font-size: 15px; }

/* ---------- Reveal on scroll ---------- */

.js [data-reveal] { opacity: 0; transform: translateY(16px); transition: opacity .6s ease, transform .6s ease; }
.js [data-reveal].is-visible { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .js [data-reveal] { opacity: 1; transform: none; transition: none; }
  .card, .btn { transition: none; }
}

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

@media (max-width: 900px) {
  section { padding: 64px 0; }
  .projects, .grid3, .features, .gallery { grid-template-columns: 1fr; }
  .card.featured { flex-direction: column; }
  .card.featured .cardMedia { min-height: 0; aspect-ratio: 16 / 10; }
  .card.featured .cardBody { padding: 24px; }
  .card.featured h3 { font-size: 26px; }
  .expGrid, .split { grid-template-columns: 1fr; gap: 32px; }
}

@media (max-width: 560px) {
  .navLinks a { padding: 6px 8px; font-size: 14px; }
  .navLinks a.hideSm { display: none; }
  .lang summary { padding: 0 8px; }
  .wordmark .name { display: none; }
  .hero { padding: 56px 0 40px; }
  .sectionHead { flex-direction: column; align-items: start; gap: 4px; }
  .specs { grid-template-columns: 1fr; }
}