@charset "utf-8";
/* =============================================================================
   niu_zh · IOI 2027 600/600
   All values resolve to tokens declared in DESIGN.md. No magic numbers.
   ========================================================================== */

/* ── 1. TOKENS ─────────────────────────────────────────────────────────── */
:root {
  /* base — blue-black */
  --ink-950: #04060b;
  --ink-900: #06080f;
  --ink-850: #080b14;
  --ink-800: #0b1020;
  --ink-750: #101729;
  --ink-700: #16203a;
  --ink-600: #1e2a48;
  --ink-500: #2b3a5e;

  /* accent — gold, the only accent hue */
  --gold-100: #fdf6e4;
  --gold-200: #f9e6b4;
  --gold-300: #f3d492;
  --gold-400: #e8c375;
  --gold-500: #d3a24e;
  --gold-600: #ab7c2c;
  --gold-700: #6f4f1b;

  /* text */
  --text-hi: #f4f1ea;
  --text-mid: #b6bccb;
  --text-lo: #808aa1;
  --text-dim: #5c657d;

  /* surfaces & effects */
  --surface-1: rgba(255, 255, 255, .030);
  --surface-2: rgba(255, 255, 255, .008);
  --hairline: rgba(232, 195, 117, .13);
  --hairline-hi: rgba(232, 195, 117, .30);
  --glow-warm: rgba(211, 162, 78, .16);
  --glow-deep: rgba(41, 62, 116, .20);
  --grain-opacity: .055;
  --grid-opacity: .06;
  --grid-size: 72px;

  --grad-gold: linear-gradient(168deg, #fdf6e4 0%, #f3d492 26%, #e8c375 52%, #d3a24e 74%, #ab7c2c 100%);
  /* 巨号数字专用：--grad-gold 的顶端接近纯白，在 300px 高的字形上会把金色「洗白」成银色，
     所以这里整条色阶都保持在饱和的金色区间内，只保留一个窄高光带。 */
  --grad-gold-hero: linear-gradient(174deg,
      #f7e2b2 0%, #efc87e 20%, #e3ae57 42%, #cf9839 64%, #b07c26 86%, #95661a 100%);
  --grad-hair: linear-gradient(160deg,
      rgba(249, 230, 180, .46), rgba(232, 195, 117, .08) 34%,
      rgba(255, 255, 255, .08) 66%, rgba(232, 195, 117, .28));

  /* type */
  --font-body: "PingFang SC", "HarmonyOS Sans SC", "Source Han Sans SC", "Noto Sans SC",
               "Microsoft YaHei", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-display: "SF Mono", "JetBrains Mono", "Cascadia Code", "Roboto Mono", ui-monospace,
                  Menlo, Consolas, "Liberation Mono", monospace;
  --font-serif: "Songti SC", "STSong", "Source Han Serif SC", "Noto Serif SC",
                "SimSun", Georgia, "Times New Roman", serif;

  --fs-score: clamp(4.25rem, 21.5vw, 19rem);
  --fs-display: clamp(3rem, 13vw, 9.5rem);
  --fs-h2: clamp(1.9rem, 4.4vw, 3.4rem);
  --fs-h3: clamp(1.15rem, 1.9vw, 1.5rem);
  --fs-year: clamp(1rem, 1.6vw, 1.3rem);
  --fs-quote: clamp(1.4rem, 3.1vw, 2.45rem);
  /* 题目卡主元素（无题名时的金色序号） */
  --fs-task-num: clamp(2.1rem, 3.6vw, 3.1rem);
  --fs-lead: clamp(1rem, 1.35vw, 1.2rem);
  --fs-body: clamp(.95rem, 1.05vw, 1.05rem);
  --fs-sm: .9rem;
  --fs-xs: .8rem;
  --fs-eyebrow: clamp(.66rem, .62rem + .18vw, .78rem);
  --fs-stat: clamp(2.6rem, 6vw, 4.4rem);

  --tracking-eyebrow: .34em;
  --tracking-tight: -.03em;
  --tracking-wide: .12em;
  --leading-body: 1.75;

  /* spacing */
  --s-1: .25rem;  --s-2: .5rem;   --s-3: .75rem;  --s-4: 1rem;
  --s-5: 1.5rem;  --s-6: 2rem;    --s-8: 3rem;    --s-10: 4rem;
  --s-12: 5rem;   --s-16: 6.5rem; --s-20: 8rem;
  --section-y: clamp(6rem, 12vh + 3rem, 12.5rem);
  --gutter: clamp(1.15rem, 4vw, 3.5rem);
  --measure: 68ch;
  --container: 1360px;
  --nav-h: clamp(3.5rem, 4.4vw, 4.5rem);
  --tl-spine: clamp(3.25rem, 5.5vw, 5rem);

  /* radii */
  --r-xs: 6px; --r-sm: 10px; --r-md: 16px; --r-lg: 24px; --r-xl: 34px; --r-pill: 999px;

  /* shadows */
  --shadow-card: 0 1px 0 rgba(255, 255, 255, .045) inset, 0 26px 60px -34px rgba(0, 0, 0, .92);
  --shadow-lift: 0 1px 0 rgba(255, 255, 255, .07) inset, 0 34px 78px -36px rgba(0, 0, 0, .96),
                 0 0 0 1px var(--hairline-hi), 0 22px 60px -40px rgba(211, 162, 78, .42);
  --shadow-deep: 0 40px 90px -50px rgba(0, 0, 0, .95);

  /* motion */
  --ease-out: cubic-bezier(.16, 1, .3, 1);
  --ease-soft: cubic-bezier(.25, 1, .5, 1);
  --ease-inout: cubic-bezier(.65, 0, .35, 1);
  --d-fast: 180ms; --d-base: 300ms; --d-slow: 520ms; --d-slower: 900ms;
  --stagger: 70ms;

  --z-bg: 0; --z-grain: 1; --z-content: 2; --z-menu: 60; --z-nav: 70;
}

/* ── 2. RESET & BASE ───────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; }

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

body {
  margin: 0;
  min-height: 100%;
  background-color: var(--ink-900);
  color: var(--text-mid);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: var(--leading-body);
  letter-spacing: .01em;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body.is-locked { overflow: hidden; }

h1, h2, h3, p, dl, dd, figure, blockquote, ol, ul { margin: 0; }
ol, ul { padding: 0; list-style: none; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
img, canvas, svg { display: block; max-width: 100%; }

::selection { background: rgba(232, 195, 117, .28); color: var(--text-hi); }

:focus-visible {
  outline: 2px solid var(--gold-300);
  outline-offset: 3px;
  border-radius: var(--r-xs);
}

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--ink-950); }
::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, var(--gold-700), var(--ink-600));
  border-radius: var(--r-pill);
  border: 3px solid var(--ink-950);
}

/* ── 3. UTILITIES ──────────────────────────────────────────────────────── */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); clip-path: inset(50%); white-space: nowrap;
}

.skip-link {
  position: fixed; top: var(--s-2); left: var(--s-2); z-index: 100;
  transform: translateY(-160%);
  padding: var(--s-2) var(--s-4);
  border-radius: var(--r-sm);
  background: var(--gold-400); color: var(--ink-900);
  font-size: var(--fs-sm); font-weight: 700;
  transition: transform var(--d-base) var(--ease-out);
}
.skip-link:focus-visible { transform: translateY(0); }

.tnum { font-variant-numeric: tabular-nums; font-feature-settings: "tnum" 1; }

.lat { font-family: var(--font-body); letter-spacing: var(--tracking-eyebrow); }

/* gold gradient text, with a solid-colour fallback for unsupporting engines */
.gold-text { color: var(--gold-400); }
@supports ((-webkit-background-clip: text) or (background-clip: text)) {
  .gold-text {
    background-image: var(--grad-gold);
    -webkit-background-clip: text;
            background-clip: text;
    color: transparent;
    -webkit-text-fill-color: transparent;
  }
}

.rule {
  display: block;
  width: clamp(2.5rem, 6vw, 5rem);
  height: 1px;
  background: linear-gradient(90deg, var(--gold-400), rgba(232, 195, 117, 0));
}

/* ── 4. BACKGROUND LAYERS ──────────────────────────────────────────────── */
.bg {
  position: fixed; inset: 0; z-index: var(--z-bg);
  pointer-events: none; overflow: hidden;
}
.bg__glow { position: absolute; display: block; }
.bg__glow--warm {
  top: -34vh; left: 50%; width: 132vw; height: 108vh; transform: translateX(-50%);
  background: radial-gradient(50% 50% at 50% 50%, var(--glow-warm) 0%, rgba(211, 162, 78, 0) 70%);
}
.bg__glow--cool {
  bottom: -32vh; left: -22vw; width: 96vw; height: 86vh;
  background: radial-gradient(50% 50% at 50% 50%, var(--glow-deep) 0%, rgba(41, 62, 116, 0) 72%);
}
.bg__grid {
  position: absolute; inset: -2px;
  background-image:
    linear-gradient(to right, rgba(198, 214, 255, var(--grid-opacity)) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(198, 214, 255, var(--grid-opacity)) 1px, transparent 1px);
  background-size: var(--grid-size) var(--grid-size);
  -webkit-mask-image: radial-gradient(130% 95% at 50% 0%, #000 0%, rgba(0, 0, 0, .45) 48%, transparent 86%);
          mask-image: radial-gradient(130% 95% at 50% 0%, #000 0%, rgba(0, 0, 0, .45) 48%, transparent 86%);
}
.bg__vignette {
  position: absolute; inset: 0;
  background: radial-gradient(120% 80% at 50% 42%, rgba(0, 0, 0, 0) 40%, var(--ink-950) 100%);
}
/* Film grain. Deliberately no blend mode: overlay/screen multiply against a
   near-black backdrop and disappear; plain low alpha reads as grain on dark. */
.bg::after {
  content: ""; position: absolute; inset: 0; pointer-events: none;
  background-image: url("data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='180'%20height='180'%3E%3Cfilter%20id='n'%3E%3CfeTurbulence%20type='fractalNoise'%20baseFrequency='.82'%20numOctaves='3'%20stitchTiles='stitch'/%3E%3C/filter%3E%3Crect%20width='180'%20height='180'%20filter='url(%23n)'%20opacity='.45'/%3E%3C/svg%3E");
  background-size: 180px 180px;
  opacity: var(--grain-opacity);
}

main, .footer { position: relative; z-index: var(--z-content); }

/* ── 5. NAV ────────────────────────────────────────────────────────────── */
.nav {
  position: fixed; inset: 0 0 auto; z-index: var(--z-nav);
  height: var(--nav-h);
  border-bottom: 1px solid transparent;
  transition: background-color var(--d-base) var(--ease-out),
              border-color var(--d-base) var(--ease-out),
              backdrop-filter var(--d-base) var(--ease-out);
}
.nav.is-scrolled {
  background-color: rgba(6, 8, 15, .74);
  -webkit-backdrop-filter: blur(14px) saturate(140%);
          backdrop-filter: blur(14px) saturate(140%);
  border-bottom-color: var(--hairline);
}
.nav__inner {
  height: 100%; width: 100%; max-width: var(--container);
  margin-inline: auto; padding-inline: var(--gutter);
  display: flex; align-items: center; gap: var(--s-5);
}
.nav__brand { display: inline-flex; align-items: center; gap: var(--s-3); margin-right: auto; }
.nav__brand-name {
  font-family: var(--font-display); font-size: 1.05rem; font-weight: 600;
  letter-spacing: -.01em; color: var(--text-hi);
}
.nav__brand-rule { width: 1px; height: 1.1em; background: var(--hairline-hi); }
.nav__brand-score {
  font-family: var(--font-display); font-size: .82rem; font-weight: 600;
  letter-spacing: var(--tracking-wide); color: var(--gold-400);
}
.nav__links { display: flex; align-items: center; gap: clamp(var(--s-4), 2.2vw, var(--s-6)); }
.nav__links a {
  position: relative; padding: var(--s-1) 0;
  font-size: var(--fs-sm); color: var(--text-lo);
  transition: color var(--d-base) var(--ease-out);
}
.nav__links a::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -2px; height: 1px;
  background: var(--grad-gold);
  transform: scaleX(0); transform-origin: left center;
  transition: transform var(--d-base) var(--ease-out);
}
.nav__links a:hover { color: var(--text-hi); }
.nav__links a:hover::after { transform: scaleX(1); }
.nav__links a.is-active { color: var(--gold-300); }
.nav__links a.is-active::after { transform: scaleX(1); }

.nav__progress {
  position: absolute; left: 0; right: 0; bottom: -1px; height: 1px;
  background: var(--hairline);
}
.nav__progress i {
  display: block; height: 100%; width: 100%;
  background: var(--grad-gold);
  box-shadow: 0 0 10px rgba(211, 162, 78, .55);
  transform: scaleX(0);
  transform-origin: left center;
}

.nav__toggle { display: none; padding: var(--s-2); margin-right: calc(var(--s-2) * -1); }
.nav__toggle-bars { display: block; width: 22px; }
.nav__toggle-bars i {
  display: block; height: 1.5px; width: 100%; background: var(--text-hi);
  transition: transform var(--d-base) var(--ease-out), opacity var(--d-fast) linear;
}
.nav__toggle-bars i + i { margin-top: 5px; }
.nav__toggle[aria-expanded="true"] .nav__toggle-bars i:nth-child(1) { transform: translateY(6.5px) rotate(45deg); }
.nav__toggle[aria-expanded="true"] .nav__toggle-bars i:nth-child(2) { opacity: 0; }
.nav__toggle[aria-expanded="true"] .nav__toggle-bars i:nth-child(3) { transform: translateY(-6.5px) rotate(-45deg); }

/* 移动端全屏菜单。顶栏 z-index 高于遮罩，汉堡按钮（关闭后变 X）始终可见可点。 */
.menu {
  position: fixed; inset: 0; z-index: var(--z-menu);
  display: grid; place-items: center;
  background: rgba(4, 6, 11, .96);
  -webkit-backdrop-filter: blur(18px);
          backdrop-filter: blur(18px);
  opacity: 0;
  transition: opacity var(--d-base) var(--ease-out);
}
.menu[hidden] { display: none; }
.menu.is-open { opacity: 1; }
.menu__inner { width: 100%; max-width: var(--container); padding: var(--gutter); }
.menu__kicker {
  font-family: var(--font-display); font-size: var(--fs-xs);
  letter-spacing: var(--tracking-eyebrow); text-transform: uppercase;
  color: var(--gold-500); margin-bottom: var(--s-6);
}
.menu__links { display: grid; gap: var(--s-2); }
.menu__links a {
  display: flex; align-items: baseline; gap: var(--s-4);
  padding: var(--s-3) 0;
  border-bottom: 1px solid var(--hairline);
  font-family: var(--font-display); font-size: clamp(1.6rem, 7vw, 2.4rem);
  color: var(--text-hi);
  transition: color var(--d-base) var(--ease-out), padding-left var(--d-base) var(--ease-out);
}
.menu__links a span { font-size: var(--fs-xs); color: var(--gold-600); letter-spacing: var(--tracking-wide); }
.menu__links a:hover, .menu__links a:focus-visible { color: var(--gold-300); padding-left: var(--s-3); }

/* ── 6. SECTION SHELL ──────────────────────────────────────────────────── */
.section {
  position: relative;
  padding-block: var(--section-y);
  scroll-margin-top: calc(var(--nav-h) + var(--s-4));
}
.section--stats, .section--journey, .section--quote {
  background: linear-gradient(180deg,
    rgba(8, 11, 20, 0) 0%, rgba(8, 11, 20, .72) 14%,
    rgba(8, 11, 20, .72) 86%, rgba(8, 11, 20, 0) 100%);
}

.shead { display: grid; gap: var(--s-3); max-width: var(--measure); margin-bottom: var(--s-10); }
.shead--split {
  grid-template-columns: minmax(0, 1.05fr) minmax(0, .95fr);
  align-items: end; gap: var(--s-6); max-width: none;
}
.shead__kicker {
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--text-lo);
}
.shead__title {
  font-size: var(--fs-h2); font-weight: 700; line-height: 1.16;
  letter-spacing: -.015em;
}
/* text-wrap: pretty 让中文末行不留单字（孤字），比手调 max-width 稳 */
.shead__deck { color: var(--text-mid); max-width: 52ch; text-wrap: pretty; }
.shead--split .shead__deck { justify-self: end; text-align: right; max-width: 44ch; }

/* ── 7. HERO ───────────────────────────────────────────────────────────── */
.hero {
  position: relative;
  min-height: 100vh;
  min-height: 100svh;
  display: flex; flex-direction: column; justify-content: center;
  padding: calc(var(--nav-h) + var(--s-10)) var(--gutter) var(--s-16);
  overflow: hidden;
  scroll-margin-top: var(--nav-h);
}
.hero__canvas {
  position: absolute; inset: 0; z-index: 0;
  width: 100%; height: 100%;
  -webkit-mask-image: radial-gradient(78% 62% at 50% 44%, #000 0%, rgba(0, 0, 0, .55) 55%, transparent 88%);
          mask-image: radial-gradient(78% 62% at 50% 44%, #000 0%, rgba(0, 0, 0, .55) 55%, transparent 88%);
}
.hero__inner {
  position: relative; z-index: 1;
  width: 100%; max-width: var(--container); margin-inline: auto;
  display: grid; grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--s-4) var(--s-5);
}
.hero__eyebrow {
  grid-column: 1 / 9;
  display: flex; align-items: center; gap: var(--s-4);
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--text-lo);
  text-wrap: balance;
}
.hero__stamp {
  grid-column: 10 / 13; justify-self: end;
  font-family: var(--font-display); font-size: var(--fs-eyebrow);
  letter-spacing: var(--tracking-wide); text-transform: uppercase; color: var(--gold-500);
}
.hero__stamp-sep { opacity: .5; margin-inline: .35em; }
.hero__name {
  grid-column: 1 / 13;
  font-family: var(--font-display); font-weight: 600;
  font-size: var(--fs-display); line-height: .9; letter-spacing: var(--tracking-tight);
}
.hero__score {
  grid-column: 1 / 13;
  display: flex; align-items: baseline; gap: var(--s-3);
  margin-top: calc(var(--s-3) * -1);
}
.hero__score-num {
  font-family: var(--font-display); font-weight: 600;
  font-size: var(--fs-score); line-height: .82; letter-spacing: -.045em;
  color: var(--gold-400);
}
/* 巨号数字用饱和金阶，避免顶部高光把金色洗成银色 */
@supports ((-webkit-background-clip: text) or (background-clip: text)) {
  .hero__score-num {
    background-image: var(--grad-gold-hero);
    -webkit-background-clip: text;
            background-clip: text;
    color: transparent;
    -webkit-text-fill-color: transparent;
  }
}
.hero__score-slash,
.hero__score-max {
  font-family: var(--font-display); font-weight: 500;
  font-size: clamp(1.25rem, 3.2vw, 2.75rem);
  color: var(--text-lo); letter-spacing: .02em;
}
.hero__score-slash { transform: translateY(-.1em); }
.hero__prose { grid-column: 6 / 13; }
.hero__prose p {
  font-size: var(--fs-lead); line-height: 1.85; color: var(--text-mid);
  max-width: 42ch; border-left: 1px solid var(--hairline); padding-left: var(--s-5);
}
.hero__actions { grid-column: 1 / 7; display: flex; flex-wrap: wrap; gap: var(--s-3); }
.hero__placard {
  grid-column: 7 / 13;
  display: flex; flex-wrap: wrap; gap: var(--s-5) clamp(var(--s-5), 3vw, var(--s-8));
  justify-content: flex-end;
}
.hero__placard-item { position: relative; padding-top: var(--s-3); }
.hero__placard-item::before {
  content: ""; position: absolute; top: 0; left: 0; right: 0; height: 1px;
  background: linear-gradient(90deg, var(--gold-500), rgba(232, 195, 117, .06));
}
.hero__placard dt {
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--text-lo);
}
.hero__placard dt .lat { color: var(--gold-700); }
.hero__placard dd {
  margin-top: var(--s-1);
  /* 用正文字体而非等宽字体：磁贴值里混有中文（题 / 分），
     等宽字体会让中西文之间出现难看的空隙。 */
  font-family: var(--font-body); font-size: 1.05rem; color: var(--text-hi);
  font-weight: 500; font-variant-numeric: tabular-nums;
}

.hero__scroll {
  position: absolute; left: var(--gutter); bottom: var(--s-6); z-index: 1;
  display: flex; align-items: center; gap: var(--s-3);
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--text-dim);
  transition: color var(--d-base) var(--ease-out);
}
.hero__scroll:hover { color: var(--gold-400); }
.hero__scroll-line {
  position: relative; display: block; width: 1px; height: 54px;
  background: var(--hairline); overflow: hidden;
}
.hero__scroll-line::after {
  content: ""; position: absolute; inset: 0;
  background: linear-gradient(180deg, transparent, var(--gold-300), transparent);
  animation: scroll-cue 2.6s var(--ease-inout) infinite;
}
@keyframes scroll-cue {
  0%   { transform: translateY(-100%); }
  60%  { transform: translateY(100%); }
  100% { transform: translateY(100%); }
}

/* ── 8. BUTTONS ────────────────────────────────────────────────────────── */
.btn {
  display: inline-flex; align-items: center; gap: var(--s-2);
  padding: .82em 1.5em; border-radius: var(--r-pill);
  font-size: var(--fs-sm); font-weight: 600; letter-spacing: .04em;
  white-space: nowrap;
  transition: transform var(--d-base) var(--ease-out),
              box-shadow var(--d-base) var(--ease-out),
              background-color var(--d-base) var(--ease-out),
              border-color var(--d-base) var(--ease-out),
              color var(--d-base) var(--ease-out);
}
.btn__icon { width: 1.05em; height: 1.05em; transition: transform var(--d-base) var(--ease-out); }
.btn:hover { transform: translateY(-2px); }
.btn:hover .btn__icon { transform: translateY(2px); }
.btn--primary {
  background-image: var(--grad-gold); color: #1a1204;
  box-shadow: 0 12px 34px -18px rgba(211, 162, 78, .7);
}
.btn--primary:hover { box-shadow: 0 18px 44px -18px rgba(211, 162, 78, .85); }
.btn--ghost {
  border: 1px solid var(--hairline-hi); color: var(--text-hi);
  background: var(--surface-1);
}
.btn--ghost:hover { border-color: var(--gold-400); background: rgba(232, 195, 117, .08); }
.btn--quiet { color: var(--text-lo); padding-inline: var(--s-2); }
.btn--quiet:hover { color: var(--gold-300); }

/* ── 9. STATS ──────────────────────────────────────────────────────────── */
.stats {
  display: grid; grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--s-4);
}
.stat {
  position: relative; overflow: hidden;
  padding: var(--s-6) var(--s-5) var(--s-5);
  border-radius: var(--r-lg);
  background: linear-gradient(168deg, var(--surface-1), var(--surface-2));
  box-shadow: var(--shadow-card);
  transition: transform var(--d-base) var(--ease-out), box-shadow var(--d-base) var(--ease-out);
}
.stat::after {
  content: ""; position: absolute; top: 0; left: var(--s-5); right: var(--s-5); height: 1px;
  background: linear-gradient(90deg, transparent, var(--gold-400), transparent);
}
.stat:hover { transform: translateY(-4px); box-shadow: var(--shadow-lift); }
.stat__label {
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--text-lo);
}
.stat__row { display: flex; align-items: baseline; gap: var(--s-2); margin-top: var(--s-3); }
.stat__value {
  font-family: var(--font-display); font-weight: 600;
  font-size: var(--fs-stat); line-height: 1; letter-spacing: -.035em;
  color: var(--text-hi);
}
.stat--accent .stat__value { color: var(--gold-400); }
.stat__unit { font-family: var(--font-display); font-size: var(--fs-h3); color: var(--gold-600); }
.stat__note { margin-top: var(--s-2); font-size: var(--fs-xs); color: var(--text-lo); }

/* ── 10. CARDS (achievements) ──────────────────────────────────────────── */
.cards { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: var(--s-6); }
.card {
  position: relative;
  display: flex; flex-direction: column;
  padding: var(--s-6) var(--s-5) var(--s-5);
  border-radius: var(--r-lg);
  background: linear-gradient(168deg, var(--surface-1), var(--surface-2));
  box-shadow: var(--shadow-card);
  transition: transform var(--d-base) var(--ease-out), box-shadow var(--d-base) var(--ease-out);
}
.card::before {
  content: ""; position: absolute; inset: 0; border-radius: inherit;
  padding: 1px; pointer-events: none;
  background: var(--grad-hair);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
          mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor; mask-composite: exclude;
  opacity: .85;
  transition: opacity var(--d-base) var(--ease-out);
}
.card:hover { transform: translateY(-5px); box-shadow: var(--shadow-lift); }
.card:hover::before { opacity: 1; }
.card__index {
  font-family: var(--font-display); font-size: var(--fs-xs);
  letter-spacing: var(--tracking-wide); color: var(--gold-600);
}
.card__label {
  margin-top: var(--s-4);
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--gold-400);
}
.card__title { margin-top: var(--s-2); font-size: var(--fs-h3); font-weight: 600; color: var(--text-hi); line-height: 1.35; }
.card__body { margin-top: var(--s-3); font-size: var(--fs-sm); color: var(--text-mid); }
.card__tags { display: flex; flex-wrap: wrap; gap: var(--s-2); margin-top: var(--s-5); }
.tag {
  font-family: var(--font-display); font-size: .68rem; letter-spacing: var(--tracking-wide);
  text-transform: uppercase; color: var(--text-lo);
  padding: .3em .7em; border-radius: var(--r-pill);
  border: 1px solid var(--hairline); background: rgba(232, 195, 117, .05);
}

/* ── 11. TIMELINE ──────────────────────────────────────────────────────── */
.timeline {
  position: relative;
  margin-top: var(--s-6);
  /* 左侧留出「年份栏 + 轴线」的装订区 */
  padding-left: calc(var(--tl-spine) + var(--s-6));
}
.timeline::before {
  content: ""; position: absolute; top: .6rem; bottom: .6rem;
  left: var(--tl-spine); width: 1px;
  background: linear-gradient(180deg,
    rgba(232, 195, 117, 0), var(--gold-500) 10%, var(--gold-300) 50%, var(--gold-600) 90%, rgba(232, 195, 117, 0));
  box-shadow: 0 0 14px rgba(211, 162, 78, .45);
}
.tl-item {
  position: relative;
  /* 正文 + 右侧边注（英文 kicker）构成两栏，撑住 1440px 下的右侧留白 */
  display: grid; grid-template-columns: minmax(0, 1fr) auto;
  column-gap: var(--s-6); align-items: start;
  padding-bottom: var(--s-10);
}
.tl-item:last-child { padding-bottom: 0; }

/* 偏移参照物是 .tl-item 自身（内容列左缘），而轴线位于内容列左侧 --s-6 处，
   年份栏则再往左 --tl-spine 并窄 --s-2，正好与轴线留出 8px 呼吸。 */
.tl-item__year {
  position: absolute; top: -.1em;
  left: calc(-1 * (var(--tl-spine) + var(--s-6)));
  width: calc(var(--tl-spine) - var(--s-2));
  text-align: right;
  font-family: var(--font-display); font-size: var(--fs-year); font-weight: 600;
  color: var(--gold-500); letter-spacing: .02em;
}
.tl-item__node {
  position: absolute; top: .45rem;
  left: calc(-1 * var(--s-6));
  width: 11px; height: 11px; margin-left: -5.5px;
  border-radius: 50%; background: var(--gold-300);
  box-shadow: 0 0 0 4px var(--ink-850), 0 0 16px rgba(232, 195, 117, .7);
}
.tl-item--final .tl-item__node { background: var(--gold-100); }
.tl-item--final .tl-item__node::after {
  content: ""; position: absolute; inset: -6px; border-radius: 50%;
  border: 1px solid var(--gold-500);
  animation: tl-pulse 2.8s var(--ease-inout) infinite;
}
@keyframes tl-pulse {
  0%   { transform: scale(.55); opacity: .9; }
  70%  { transform: scale(1.6); opacity: 0; }
  100% { transform: scale(1.6); opacity: 0; }
}
.tl-item__kicker {
  grid-column: 2; grid-row: 1;
  text-align: right; padding-top: .1em;
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--gold-500);
  white-space: nowrap;
}
.tl-item__main { grid-column: 1; grid-row: 1; min-width: 0; }
.tl-item__title { margin-top: var(--s-2); font-size: var(--fs-h3); font-weight: 600; color: var(--text-hi); }
.tl-item__body { margin-top: var(--s-2); font-size: var(--fs-sm); color: var(--text-mid); max-width: 56ch; }

/* ── 12. PROBLEMS ──────────────────────────────────────────────────────── */
.pgroup + .pgroup { margin-top: var(--s-12); }
.pgroup__head { display: flex; align-items: center; gap: var(--s-4); margin-bottom: var(--s-5); }
.pgroup__day {
  font-family: var(--font-display); font-size: var(--fs-h3); font-weight: 600;
  color: var(--gold-400); letter-spacing: var(--tracking-wide);
}
.pgroup__label {
  font-size: var(--fs-eyebrow); text-transform: uppercase;
  letter-spacing: var(--tracking-eyebrow); color: var(--text-lo);
}
.pgroup__line { flex: 1; height: 1px; background: linear-gradient(90deg, var(--hairline), transparent); }
.pgroup__grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: var(--s-4); }

/* 卡片节奏（题目墙）：题名与摘要默认都不渲染，主元素是金色序号。
   上下内边距比 .card 略大、gap 略松，好让「序号 + 细线 + 刻度条」
   这三段在去掉正文后仍读起来是刻意排布的牌面，而不是空掉的卡壳。 */
.task {
  position: relative;
  display: flex; flex-direction: column; gap: var(--s-4);
  padding: var(--s-6) var(--s-5) var(--s-5);
  border-radius: var(--r-md);
  background: linear-gradient(168deg, var(--surface-1), var(--surface-2));
  box-shadow: var(--shadow-card);
  transition: transform var(--d-base) var(--ease-out), box-shadow var(--d-base) var(--ease-out);
}
.task::before {
  content: ""; position: absolute; inset: 0; border-radius: inherit;
  padding: 1px; pointer-events: none; background: var(--grad-hair);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
          mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor; mask-composite: exclude;
  opacity: .7; transition: opacity var(--d-base) var(--ease-out);
}
.task:hover { transform: translateY(-4px); box-shadow: var(--shadow-lift); }
.task:hover::before { opacity: 1; }
.task__top { display: flex; align-items: center; justify-content: space-between; gap: var(--s-3); }
.task__id {
  font-family: var(--font-display); font-size: var(--fs-eyebrow);
  letter-spacing: var(--tracking-wide); text-transform: uppercase; color: var(--text-lo);
}
.badge {
  font-family: var(--font-display); font-size: var(--fs-xs); font-weight: 600;
  letter-spacing: .04em; white-space: nowrap;
  padding: .22em .68em; border-radius: var(--r-pill);
  color: var(--gold-200);
  border: 1px solid var(--hairline-hi);
  background: rgba(211, 162, 78, .12);
}
/* 卡片主元素，二选一：
   1) task__title  —— SITE_DATA 里填了 title 时使用（填回真实题名即生效）
   2) task__num    —— 默认的金色序号，作为无题名时的视觉锚点（aria-hidden，
                      真实信息由同卡片内的 .sr-only 承担） */
.task__title { font-size: var(--fs-h3); font-weight: 600; color: var(--text-hi); line-height: 1.3; }
.task__num {
  font-family: var(--font-display); font-weight: 600;
  font-size: var(--fs-task-num); line-height: 1; letter-spacing: -.04em;
  color: var(--gold-400);
}
/* 序号与刻度条之间的短金线，复用 .rule 渐变，给牌面一个中段结构 */
.task__rule { width: clamp(2rem, 4vw, 3rem); }
/* 摘要：SITE_DATA 的 abstract 为空时不会渲染此元素。
   规则保留在样式表里，用户填回 abstract 即可直接生效，无需改 CSS。 */
.task__abstract { font-size: var(--fs-sm); color: var(--text-mid); }
/* margin-top:auto 把刻度条压到卡片底部，始终与下内边距齐平 */
.ticks { display: flex; gap: 3px; margin-top: auto; padding-top: var(--s-3); }
.ticks i { flex: 1; height: 2px; background: linear-gradient(90deg, var(--gold-600), var(--gold-300)); }

/* ── 13. QUOTE ─────────────────────────────────────────────────────────── */
.quote {
  position: relative;
  max-width: 48rem; margin-inline: auto; text-align: center;
  padding-block: var(--s-8);
}
.quote::before, .quote::after {
  content: ""; position: absolute; top: 12%; bottom: 12%; width: 1px;
  background: linear-gradient(180deg, transparent, var(--hairline-hi), transparent);
}
/* 左右装饰竖线位于引文块外侧 --s-10，视口不够宽时会溢出屏幕，
   所以仅在 ≥1081px 显示（1081px 起外侧仍有富余空间）。 */
.quote::before { left: calc(-1 * var(--s-10)); }
.quote::after { right: calc(-1 * var(--s-10)); }
.quote__glyph {
  display: block; height: .5em; overflow: hidden;
  font-family: var(--font-serif); font-size: clamp(5rem, 13vw, 10rem);
  line-height: 1; color: var(--gold-500); opacity: .55;
}
.quote__body {
  font-family: var(--font-serif); font-size: var(--fs-quote);
  line-height: 1.7; color: var(--text-hi); letter-spacing: .015em;
}
.quote__cite {
  margin-top: var(--s-6);
  font-family: var(--font-display); font-size: var(--fs-xs);
  text-transform: uppercase; letter-spacing: .22em; color: var(--text-lo);
}

/* ── 14. FOOTER ────────────────────────────────────────────────────────── */
.footer { border-top: 1px solid var(--hairline); }
.footer__inner {
  display: flex; flex-wrap: wrap; align-items: center;
  justify-content: space-between; gap: var(--s-5);
  padding-block: var(--s-8);
}
.footer__mark { display: flex; align-items: center; gap: var(--s-3); }
.footer__mark-name { font-family: var(--font-display); font-size: 1.05rem; font-weight: 600; color: var(--text-hi); }
.footer__mark-rule { width: 1px; height: 1.1em; background: var(--hairline-hi); }
.footer__mark-score { font-family: var(--font-display); font-size: .95rem; letter-spacing: .04em; }
.footer__note { font-size: var(--fs-xs); color: var(--text-lo); }
.footer__links { display: flex; flex-wrap: wrap; gap: var(--s-5); }
.footer__links a {
  display: inline-flex; align-items: center; gap: var(--s-2);
  font-family: var(--font-display); font-size: var(--fs-xs);
  letter-spacing: var(--tracking-wide); text-transform: uppercase;
  color: var(--text-lo);
  transition: color var(--d-base) var(--ease-out);
}
.footer__links a:hover { color: var(--gold-300); }
.footer__links a svg { width: .95em; height: .95em; }
.footer__fineprint {
  padding: var(--s-5) var(--gutter) var(--s-8);
  text-align: center; font-size: var(--fs-xs); color: var(--text-dim);
}

/* ── 15. REVEAL ────────────────────────────────────────────────────────── */
.reveal {
  opacity: 0;
  transform: translate3d(0, 22px, 0);
  transition: opacity var(--d-slow) var(--ease-out), transform var(--d-slow) var(--ease-out);
}
.reveal.is-in { opacity: 1; transform: none; }

/* ── 16. NO-JS FALLBACK LISTS ──────────────────────────────────────────── */
.noscript-list {
  display: grid; gap: var(--s-2);
  margin-top: var(--s-6); padding: var(--s-5);
  border: 1px solid var(--hairline); border-radius: var(--r-md);
  background: var(--surface-1);
  font-size: var(--fs-sm); color: var(--text-mid);
}
.noscript-list li { padding-left: var(--s-4); position: relative; }
.noscript-list li::before {
  content: ""; position: absolute; left: 0; top: .7em;
  width: 5px; height: 5px; border-radius: 50%; background: var(--gold-500);
}

/* ── 17. RESPONSIVE ────────────────────────────────────────────────────── */
@media (max-width: 1080px) {
  .cards, .pgroup__grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .hero__prose { grid-column: 5 / 13; }
  .hero__actions { grid-column: 1 / 8; }
  .hero__placard { grid-column: 8 / 13; }
  /* 右侧边注列在窄屏放不下了，折回正文上方 */
  .tl-item { grid-template-columns: minmax(0, 1fr); }
  .tl-item__kicker {
    grid-column: 1; grid-row: 2; text-align: left; padding-top: 0;
    margin-top: var(--s-2);
  }
  .tl-item__main { grid-column: 1; grid-row: 3; }
  /* 见 .quote::before 注释：窄于此宽度时引文外侧竖线会造成横向溢出 */
  .quote::before, .quote::after { display: none; }
}

@media (max-width: 900px) {
  .nav__links { display: none; }
  .nav__toggle { display: block; }
  .shead--split { grid-template-columns: minmax(0, 1fr); align-items: start; gap: var(--s-3); }
  .shead--split .shead__deck { justify-self: start; text-align: left; }
  .hero__inner { grid-template-columns: minmax(0, 1fr); gap: var(--s-4); }
  .hero__eyebrow, .hero__stamp, .hero__name, .hero__score,
  .hero__prose, .hero__actions, .hero__placard { grid-column: 1 / -1; }
  .hero__stamp { justify-self: start; margin-top: calc(var(--s-2) * -1); }
  .hero__prose p { max-width: none; }
  .hero__actions { margin-top: var(--s-2); }
  .hero__placard { justify-content: flex-start; }
}

@media (max-width: 720px) {
  :root {
    --tl-spine: 10px;
    /* 眉题字母间距在窄屏收窄，否则「INTERNATIONAL OLYMPIAD IN INFORMATICS」会折行 */
    --tracking-eyebrow: .2em;
  }
  .cards, .pgroup__grid, .stats { grid-template-columns: minmax(0, 1fr); }
  .stat { padding: var(--s-5) var(--s-5) var(--s-4); }
  .hero { padding-bottom: var(--s-12); }
  .hero__scroll { display: none; }
  .hero__placard { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-4); }
  /* 年份栏宽度已不足，退回内容列并显式指定网格行，避免自动放置跑到正文之后 */
  .tl-item__year {
    position: static; grid-column: 1; grid-row: 1;
    width: auto; text-align: left; margin-bottom: var(--s-1);
  }
  .tl-item__kicker { grid-row: 2; }
  .tl-item__node { top: .35rem; }
  .footer__inner { flex-direction: column; align-items: flex-start; }
}

@media (max-width: 420px) {
  :root { --fs-body: .95rem; }
  .hero__actions .btn { flex: 1 1 auto; justify-content: center; }
  .hero__placard { gap: var(--s-4); }
  /* 320px 下这串英文必然折行：让两行长度均衡（balance），
     并让出装饰性金线，避免出现只剩一个词的孤行。 */
  .hero__eyebrow .rule { display: none; }
}

/* ── 18. PRINT ─────────────────────────────────────────────────────────
   打印 / 存 PDF 时浏览器不会滚动，IntersectionObserver 不会触发，
   所以必须强制显示所有滚动揭示内容，并去掉固定层与画布。 */
@media print {
  .nav, .menu, .hero__canvas, .hero__scroll, .bg, .skip-link { display: none !important; }
  .reveal { opacity: 1 !important; transform: none !important; }
  body { background: var(--ink-900); }
  .section { padding-block: var(--s-8); break-inside: avoid; }
  .card, .stat, .task, .tl-item { break-inside: avoid; }
}

/* ── 19. REDUCED MOTION ────────────────────────────────────────────────── */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    scroll-behavior: auto !important;
  }
  .reveal { opacity: 1; transform: none; }
  .hero__scroll-line::after { animation: none; opacity: .5; }
  .tl-item--final .tl-item__node::after { display: none; }
  .card:hover, .task:hover, .stat:hover, .btn:hover { transform: none; }
}