/* Итератор — образовательный портал по компьютерным наукам.
   Один стилевой файл, без внешних шрифтов и библиотек. */

:root {
  --bg: #ffffff;
  --bg-soft: #f5f8fd;
  --bg-tint: #eef4fe;
  --ink: #0f1729;
  --ink-2: #44506b;
  --ink-3: #74809a;
  --line: #e3e9f3;
  --line-2: #ccd5e6;
  --blue: #2563eb;
  --blue-dark: #1d4ed8;
  --blue-soft: #dbe7fe;
  --cyan: #0891b2;
  --cyan-soft: #cffafe;
  --violet: #7c3aed;
  --violet-soft: #ede9fe;
  --amber: #d97706;
  --amber-soft: #fef3c7;
  --green: #15803d;
  --green-soft: #dcfce7;
  --rose: #be123c;
  --rose-soft: #ffe4e6;
  --night: #0b1222;
  --night-2: #141d33;
  --r: 14px;
  --r-sm: 9px;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --sh-sm: 0 1px 2px rgba(15,23,41,.06), 0 2px 8px -4px rgba(15,23,41,.10);
  --sh: 0 2px 4px rgba(15,23,41,.05), 0 14px 32px -16px rgba(15,23,41,.22);
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 92px; -webkit-text-size-adjust: 100%; }

body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 16.5px/1.68 var(--sans); -webkit-font-smoothing: antialiased;
}

img, svg { display: block; max-width: 100%; }
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 2px; }
:focus-visible { outline: 3px solid var(--blue); outline-offset: 2px; border-radius: 4px; }

h1, h2, h3, h4 { margin: 0 0 .5em; font-weight: 750; letter-spacing: -0.03em; line-height: 1.16; color: var(--ink); }
h1 { font-size: clamp(2.1rem, 4.6vw, 3.3rem); letter-spacing: -0.04em; }
h2 { font-size: clamp(1.5rem, 2.8vw, 2.2rem); }
h3 { font-size: 1.16rem; }
h4 { font-size: 1rem; }
p { margin: 0 0 1.1em; max-width: 72ch; }
ul, ol { margin: 0 0 1.2em; padding-left: 1.3em; }
li { margin-bottom: .45em; }
li::marker { color: var(--ink-3); }
hr { border: 0; border-top: 1px solid var(--line); margin: 2.4rem 0; }

code {
  font-family: var(--mono); font-size: .88em; background: var(--bg-soft);
  border: 1px solid var(--line); padding: .1em .38em; border-radius: 5px;
}
pre {
  margin: 0 0 1.4em; padding: 18px 20px; overflow-x: auto; background: var(--night);
  color: #d7dced; border-radius: var(--r-sm); font-family: var(--mono);
  font-size: .85rem; line-height: 1.62;
}
pre code { background: none; border: 0; padding: 0; color: inherit; font-size: inherit; }
.k { color: #a5b4fc; } .s { color: #86efac; } .n { color: #fcd34d; }
.c { color: #7b8aa8; font-style: italic; } .f { color: #67e8f9; }

.wrap { width: 100%; max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.narrow { max-width: 790px; }
.skip { position: absolute; left: -9999px; background: var(--blue); color: #fff; padding: 11px 16px; z-index: 99; }
.skip:focus { left: 0; top: 0; }

/* ---------- Шапка ---------- */
.hdr {
  position: sticky; top: 0; z-index: 50; background: rgba(255,255,255,.92);
  backdrop-filter: saturate(160%) blur(12px); border-bottom: 1px solid var(--line);
}
.hdr__in { display: flex; align-items: center; gap: 28px; min-height: 68px; }
.brand { display: inline-flex; align-items: center; gap: 11px; color: var(--ink); font-weight: 800; font-size: 1.14rem; letter-spacing: -0.035em; flex: none; }
.brand:hover { text-decoration: none; }
.nav { margin-left: auto; display: flex; align-items: center; gap: 26px; flex-wrap: wrap; }
.nav a { color: var(--ink-2); font-size: .94rem; font-weight: 550; }
.nav a:hover { color: var(--ink); text-decoration: none; }
.nav a[aria-current="page"] { color: var(--blue); font-weight: 650; }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 11px 20px; border-radius: 100px; font-size: .94rem; font-weight: 650;
  background: var(--blue); color: #fff; border: 1.5px solid var(--blue); cursor: pointer;
}
.btn:hover { background: var(--blue-dark); border-color: var(--blue-dark); color: #fff; text-decoration: none; }
.btn--sec { background: #fff; color: var(--ink); border-color: var(--line-2); }
.btn--sec:hover { background: var(--bg-soft); color: var(--ink); border-color: var(--ink-3); }
.btn--night { background: #fff; color: var(--night); border-color: #fff; }
.btn--night:hover { background: var(--blue-soft); border-color: var(--blue-soft); color: var(--night); }
.btn--outNight { background: transparent; color: #fff; border-color: rgba(255,255,255,.4); }
.btn--outNight:hover { background: rgba(255,255,255,.12); color: #fff; border-color: rgba(255,255,255,.7); }
.btn--lg { padding: 14px 26px; font-size: 1.02rem; }

/* ---------- Секции ---------- */
section { padding: 76px 0; }
.soft { background: var(--bg-soft); }
.night { background: var(--night); color: #a9b4cc; }
.night h1, .night h2, .night h3 { color: #fff; }
.night p { color: #9aa6c0; }

.eyebrow { display: inline-flex; align-items: center; gap: 8px; font-size: .76rem; font-weight: 750; letter-spacing: .13em; text-transform: uppercase; color: var(--blue); margin-bottom: 14px; }
.night .eyebrow { color: #93c5fd; }
.lead { font-size: 1.1rem; color: var(--ink-2); max-width: 64ch; }
.night .lead { color: #a9b4cc; }

.grid { display: grid; gap: 24px; }
.g2 { grid-template-columns: repeat(2, minmax(0,1fr)); }
.g3 { grid-template-columns: repeat(3, minmax(0,1fr)); }
.g4 { grid-template-columns: repeat(4, minmax(0,1fr)); }
.split { display: grid; grid-template-columns: 1.08fr .92fr; gap: 60px; align-items: center; }

/* ---------- Главный экран ---------- */
.hero { padding: clamp(56px, 7vw, 96px) 0 clamp(48px, 6vw, 84px); background:
  radial-gradient(1100px 420px at 12% -8%, var(--bg-tint) 0%, rgba(255,255,255,0) 62%),
  radial-gradient(760px 340px at 92% 4%, var(--cyan-soft) 0%, rgba(255,255,255,0) 58%); }
.hero h1 { max-width: 17ch; margin-bottom: 20px; }
.hero .lead { font-size: 1.18rem; }
.hero__cta { display: flex; flex-wrap: wrap; gap: 13px; margin-top: 30px; }
.hero__note { margin-top: 20px; font-size: .9rem; color: var(--ink-3); }
.ribbon {
  display: inline-flex; align-items: center; gap: 9px; margin-bottom: 20px; padding: 6px 14px 6px 7px;
  background: #fff; border: 1px solid var(--line); border-radius: 100px; font-size: .84rem; color: var(--ink-2); box-shadow: var(--sh-sm);
}
.ribbon b { background: var(--green-soft); color: var(--green); padding: 2px 9px; border-radius: 100px; font-size: .74rem; font-weight: 750; }

.pagehead { padding: clamp(48px,6vw,80px) 0 clamp(32px,4vw,52px); background: var(--bg-soft); border-bottom: 1px solid var(--line); }
.pagehead h1 { max-width: 20ch; }
.crumbs { font-size: .84rem; color: var(--ink-3); margin-bottom: 18px; }
.crumbs span { padding: 0 8px; opacity: .6; }

/* ---------- Карточки ---------- */
.card { background: #fff; border: 1px solid var(--line); border-radius: var(--r); padding: 26px; }
.card h3 { margin-bottom: 8px; }
.card p { font-size: .95rem; color: var(--ink-2); margin-bottom: 0; }
.card--lift { box-shadow: var(--sh-sm); transition: box-shadow .18s ease, transform .18s ease; }
.card--lift:hover { box-shadow: var(--sh); transform: translateY(-2px); }
.night .card { background: var(--night-2); border-color: #22304d; }
.night .card p { color: #93a0bb; }

.ico { width: 44px; height: 44px; border-radius: 12px; display: grid; place-items: center; margin-bottom: 16px; }
.ico svg { width: 22px; height: 22px; stroke-width: 1.9; }
.ico--blue { background: var(--blue-soft); color: var(--blue); }
.ico--cyan { background: var(--cyan-soft); color: var(--cyan); }
.ico--violet { background: var(--violet-soft); color: var(--violet); }
.ico--amber { background: var(--amber-soft); color: var(--amber); }
.ico--green { background: var(--green-soft); color: var(--green); }
.ico--rose { background: var(--rose-soft); color: var(--rose); }

.tag {
  display: inline-block; padding: 4px 11px; margin: 0 6px 6px 0; border-radius: 100px;
  font-size: .78rem; font-weight: 600; background: var(--bg-soft); color: var(--ink-2); border: 1px solid var(--line);
}
.tag--blue { background: var(--blue-soft); color: var(--blue-dark); border-color: transparent; }
.tag--green { background: var(--green-soft); color: var(--green); border-color: transparent; }
.tag--amber { background: var(--amber-soft); color: var(--amber); border-color: transparent; }
.tag--violet { background: var(--violet-soft); color: var(--violet); border-color: transparent; }

.stat b { display: block; font-size: clamp(2rem,3.6vw,2.7rem); font-weight: 800; letter-spacing: -0.045em; line-height: 1.04; }
.stat span { display: block; margin-top: 8px; font-size: .9rem; color: var(--ink-3); }
.night .stat b { color: #fff; }
.night .stat span { color: #8d9ab6; }

/* ---------- Направления ---------- */
.track { display: block; color: inherit; background: #fff; border: 1px solid var(--line); border-radius: var(--r); padding: 28px; box-shadow: var(--sh-sm); }
.track:hover { text-decoration: none; box-shadow: var(--sh); }
.track:hover h3 { color: var(--blue); }
.track__top { display: flex; align-items: flex-start; justify-content: space-between; gap: 16px; }
.track__lvl { font-size: .74rem; font-weight: 750; letter-spacing: .08em; text-transform: uppercase; color: var(--ink-3); white-space: nowrap; padding-top: 6px; }
.track p { color: var(--ink-2); font-size: .95rem; }
.track__foot { display: flex; flex-wrap: wrap; gap: 18px; margin-top: 18px; padding-top: 16px; border-top: 1px solid var(--line); font-size: .85rem; color: var(--ink-3); }
.track__foot b { color: var(--ink); font-weight: 650; }

.bar { height: 7px; border-radius: 100px; background: var(--line); overflow: hidden; margin: 14px 0 0; }
.bar i { display: block; height: 100%; border-radius: 100px; background: var(--blue); }

/* ---------- Программа ---------- */
.mod { display: grid; grid-template-columns: 58px minmax(0,1fr); gap: 24px; padding: 26px 0; border-top: 1px solid var(--line); }
.mod:last-of-type { border-bottom: 1px solid var(--line); }
.mod__n {
  width: 44px; height: 44px; border-radius: 12px; background: var(--bg-tint); color: var(--blue);
  display: grid; place-items: center; font-weight: 800; font-size: 1rem; font-family: var(--mono);
}
.mod h3 { margin-bottom: 7px; }
.mod p { font-size: .96rem; color: var(--ink-2); margin-bottom: 10px; }
.mod__meta { font-size: .84rem; color: var(--ink-3); }

details { border-top: 1px solid var(--line); padding: 16px 0; }
details:last-of-type { border-bottom: 1px solid var(--line); }
summary { cursor: pointer; font-weight: 650; list-style: none; display: flex; justify-content: space-between; gap: 18px; align-items: center; }
summary::-webkit-details-marker { display: none; }
summary::after { content: "+"; color: var(--blue); font-size: 1.35rem; line-height: 1; font-weight: 400; }
details[open] summary::after { content: "–"; }
details p { margin: 12px 0 0; color: var(--ink-2); font-size: .96rem; }

/* ---------- Библиотека ---------- */
.art { display: block; color: inherit; border-top: 1px solid var(--line); padding: 26px 0; }
.art:last-of-type { border-bottom: 1px solid var(--line); }
.art:hover { text-decoration: none; }
.art:hover h3 { color: var(--blue); }
.art__meta { display: flex; flex-wrap: wrap; gap: 14px; font-size: .82rem; color: var(--ink-3); margin-bottom: 10px; align-items: center; }
.art p { color: var(--ink-2); font-size: .96rem; margin: 0; }

.prose { max-width: 70ch; }
.prose h2 { margin-top: 2.2em; scroll-margin-top: 92px; }
.prose h3 { margin-top: 1.7em; scroll-margin-top: 92px; }
.prose figure { margin: 2.2rem 0; }
.prose figcaption { margin-top: 10px; font-size: .86rem; color: var(--ink-3); }
.callout { background: var(--bg-tint); border-radius: var(--r); padding: 20px 24px; margin: 0 0 1.5em; border-left: 4px solid var(--blue); }
.callout b { display: block; font-size: .78rem; letter-spacing: .1em; text-transform: uppercase; color: var(--blue); margin-bottom: 7px; }
.callout p:last-child { margin-bottom: 0; }
.callout--amber { background: var(--amber-soft); border-left-color: var(--amber); }
.callout--amber b { color: var(--amber); }

table { width: 100%; border-collapse: collapse; font-size: .93rem; margin: 0 0 1.5em; display: block; overflow-x: auto; }
th, td { text-align: left; padding: 11px 14px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font-size: .74rem; letter-spacing: .1em; text-transform: uppercase; color: var(--ink-3); background: var(--bg-soft); white-space: nowrap; }

/* ---------- Глоссарий ---------- */
.alpha { display: flex; flex-wrap: wrap; gap: 6px; margin: 0 0 40px; }
.alpha a {
  display: grid; place-items: center; min-width: 38px; height: 38px; padding: 0 9px;
  border: 1px solid var(--line); border-radius: var(--r-sm); background: #fff;
  font-weight: 650; font-size: .92rem; color: var(--ink-2);
}
.alpha a:hover { background: var(--blue); color: #fff; border-color: var(--blue); text-decoration: none; }
.gl-letter { font-family: var(--mono); font-size: 1.5rem; font-weight: 800; color: var(--blue); margin: 48px 0 16px; scroll-margin-top: 92px; }
.gl-letter:first-of-type { margin-top: 0; }
.term { border-top: 1px solid var(--line); padding: 20px 0; }
.term h3 { margin-bottom: 4px; font-size: 1.05rem; }
.term__en { font-family: var(--mono); font-size: .84rem; color: var(--ink-3); margin-bottom: 8px; }
.term p { font-size: .96rem; color: var(--ink-2); margin: 0; }
.term p + p { margin-top: .7em; }

/* ---------- Подвал ---------- */
.ftr { background: var(--night); color: #8d9ab6; padding: 68px 0 34px; font-size: .92rem; }
.ftr a { color: #c3cce0; }
.ftr a:hover { color: #fff; }
.ftr__grid { display: grid; grid-template-columns: 1.7fr 1fr 1fr 1fr; gap: 38px; }
.ftr h4 { color: #fff; font-size: .73rem; letter-spacing: .15em; text-transform: uppercase; margin-bottom: 15px; }
.ftr ul { list-style: none; margin: 0; padding: 0; }
.ftr li { margin-bottom: 9px; }
.ftr__brand { display: inline-flex; align-items: center; gap: 10px; color: #fff; font-weight: 800; font-size: 1.1rem; margin-bottom: 13px; letter-spacing: -0.03em; }
.ftr__bottom { margin-top: 52px; padding-top: 22px; border-top: 1px solid #22304d; display: flex; flex-wrap: wrap; gap: 14px; justify-content: space-between; font-size: .84rem; }

/* ---------- 404 ---------- */
.nf { min-height: 72vh; display: grid; place-items: center; padding: 60px 0; background:
  radial-gradient(900px 380px at 50% 0%, var(--bg-tint) 0%, rgba(255,255,255,0) 65%); }
.nf__in { text-align: center; }
.nf__code { font-family: var(--mono); font-size: clamp(3.6rem,13vw,7rem); font-weight: 800; letter-spacing: -0.05em; line-height: 1; color: var(--blue); }
.nf p { margin-left: auto; margin-right: auto; }
.nf .links { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; margin-top: 28px; }

/* ---------- Адаптив ---------- */
@media (max-width: 1040px) {
  .split { grid-template-columns: 1fr; gap: 40px; }
  .g4 { grid-template-columns: repeat(2, minmax(0,1fr)); }
  .ftr__grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 800px) {
  body { font-size: 16px; }
  section { padding: 56px 0; }
  .hdr { position: static; }
  .hdr__in { flex-wrap: wrap; min-height: 0; padding: 12px 0; gap: 12px 20px; }
  .nav { margin-left: 0; width: 100%; gap: 18px; font-size: .9rem; }
  .g2, .g3 { grid-template-columns: 1fr; }
  .mod { grid-template-columns: 1fr; gap: 12px; }
  .track__top { flex-direction: column; gap: 6px; }
  .track__lvl { padding-top: 0; }
}
@media (max-width: 430px) {
  .g4 { grid-template-columns: 1fr; }
  .ftr__grid { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}