/* ===== Задания ЕГЭ — styles ===== */
:root{
  --bg:#ffffff;
  --ink:#141726;
  --ink-soft:#4b5168;
  --ink-mute:#8990a6;
  --line:#eceef4;
  --line-2:#e2e5ef;
  --card:#ffffff;
  --violet:#5b5bd6;
  --violet-2:#7c6cf0;
  --blue:#3b82f6;
  --grad:linear-gradient(120deg,#6366f1 0%,#7c6cf0 45%,#3b82f6 100%);
  --grad-soft:linear-gradient(120deg,#eef0ff 0%,#eaf2ff 100%);
  --ok:#12a150;
  --ok-bg:#e8f8ef;
  --shadow-sm:0 1px 2px rgba(20,23,38,.05),0 2px 8px rgba(20,23,38,.05);
  --shadow-md:0 8px 24px rgba(37,42,73,.09);
  --shadow-lg:0 18px 48px rgba(37,42,73,.14);
  --r-lg:20px; --r-md:14px; --r-sm:10px;
  --maxw:960px;
}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0; background:var(--bg); color:var(--ink);
  font-family:'Segoe UI',system-ui,-apple-system,Roboto,'Helvetica Neue',Arial,sans-serif;
  font-size:17px; line-height:1.6; -webkit-font-smoothing:antialiased;
  overflow-x:hidden;
}
a{color:inherit;text-decoration:none}
img{max-width:100%;height:auto;display:block}
button{font-family:inherit}

/* ===== Header ===== */
.site-header{
  position:sticky; top:0; z-index:60;
  background:rgba(255,255,255,.82); backdrop-filter:saturate(180%) blur(14px);
  border-bottom:1px solid var(--line);
  transition:box-shadow .3s;
}
.site-header.scrolled{box-shadow:0 6px 24px rgba(30,34,60,.07)}
.header-inner{
  max-width:1180px; margin:0 auto; padding:0 20px;
  height:66px; display:flex; align-items:center; gap:22px;
}
.brand{display:flex;align-items:center;gap:11px;font-weight:800;font-size:20px;letter-spacing:-.01em;flex-shrink:0}
.brand-mark{
  display:grid;place-items:center;width:38px;height:38px;border-radius:11px;
  background:var(--grad); color:#fff; font-size:13px; font-weight:800; letter-spacing:.02em;
  box-shadow:0 6px 16px rgba(99,102,241,.4);
}
.brand-accent{background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.subject-nav{display:flex;gap:4px;margin-left:auto;flex-wrap:wrap}
.subject-nav a{
  position:relative;padding:9px 15px;border-radius:10px;font-size:15px;font-weight:600;
  color:var(--ink-soft);transition:color .2s,background .2s;white-space:nowrap;
}
.subject-nav a:hover{color:var(--violet);background:var(--grad-soft)}
.subject-nav a.active{color:#fff;background:var(--grad);box-shadow:0 6px 16px rgba(99,102,241,.32)}

.nav-toggle{display:none;flex-direction:column;gap:5px;margin-left:auto;
  width:44px;height:44px;border:1px solid var(--line-2);border-radius:11px;background:#fff;cursor:pointer;align-items:center;justify-content:center}
.nav-toggle span{width:20px;height:2px;background:var(--ink);border-radius:2px;transition:.3s}
.nav-toggle[aria-expanded="true"] span:nth-child(1){transform:translateY(7px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] span:nth-child(2){opacity:0}
.nav-toggle[aria-expanded="true"] span:nth-child(3){transform:translateY(-7px) rotate(-45deg)}

/* ===== Hero ===== */
.hero{position:relative;overflow:hidden}
.hero-bg{position:absolute;inset:0;z-index:0;pointer-events:none}
.blob{position:absolute;border-radius:50%;filter:blur(60px);opacity:.5;animation:float 16s ease-in-out infinite}
.blob-1{width:420px;height:420px;background:#c7d2fe;top:-160px;left:-120px}
.blob-2{width:380px;height:380px;background:#ddd6fe;top:-80px;right:-120px;animation-delay:-5s}
.blob-3{width:320px;height:320px;background:#bfdbfe;top:120px;left:40%;animation-delay:-9s}
@keyframes float{0%,100%{transform:translate(0,0) scale(1)}33%{transform:translate(30px,-25px) scale(1.06)}66%{transform:translate(-20px,20px) scale(.96)}}

.hero-inner{position:relative;z-index:1;max-width:var(--maxw);margin:0 auto;padding:74px 20px 30px;text-align:center}
.hero-eyebrow{
  display:inline-block;margin:0 0 18px;padding:7px 16px;border-radius:100px;
  background:#fff;border:1px solid var(--line-2);box-shadow:var(--shadow-sm);
  font-size:14px;font-weight:700;color:var(--violet);letter-spacing:.02em;
  animation:pop .6s .05s both;
}
.hero-title{
  margin:0 0 20px;font-size:clamp(34px,6vw,58px);line-height:1.08;font-weight:800;letter-spacing:-.02em;
  animation:rise .7s .1s both;
}
.hero-sub{
  max-width:620px;margin:0 auto 40px;font-size:clamp(16px,2.2vw,19px);color:var(--ink-soft);
  animation:rise .7s .2s both;
}

.subject-cards{
  display:grid;grid-template-columns:repeat(4,1fr);gap:16px;text-align:left;
  animation:rise .7s .3s both;
}
.subject-card{
  position:relative;display:flex;flex-direction:column;gap:10px;
  padding:22px 20px;border-radius:var(--r-lg);background:var(--card);
  border:1px solid var(--line);box-shadow:var(--shadow-sm);cursor:pointer;overflow:hidden;
  transition:transform .28s cubic-bezier(.2,.7,.3,1),box-shadow .28s,border-color .28s;
  text-align:left;font:inherit;color:inherit;
}
.subject-card::before{content:"";position:absolute;inset:0 0 auto 0;height:4px;background:var(--grad);transform:scaleX(0);transform-origin:left;transition:transform .3s}
.subject-card:hover{transform:translateY(-6px);box-shadow:var(--shadow-lg);border-color:transparent}
.subject-card:hover::before{transform:scaleX(1)}
.sc-icon{width:46px;height:46px;border-radius:13px;display:grid;place-items:center;font-size:24px;background:var(--grad-soft)}
.sc-name{font-size:19px;font-weight:800;letter-spacing:-.01em}
.sc-meta{font-size:14px;color:var(--ink-mute);font-weight:600}
.sc-go{margin-top:auto;display:inline-flex;align-items:center;gap:6px;font-size:14.5px;font-weight:700;color:var(--violet)}
.sc-go svg{transition:transform .25s}
.subject-card:hover .sc-go svg{transform:translateX(4px)}

/* ===== SEO intro ===== */
.seo-intro{max-width:var(--maxw);margin:12px auto 0;padding:40px 20px 10px}
.seo-intro h2{font-size:clamp(23px,3.4vw,30px);letter-spacing:-.01em;margin:0 0 14px}
.seo-intro p{color:var(--ink-soft);margin:0 0 18px}
.seo-points{list-style:none;padding:0;margin:0;display:grid;gap:10px}
.seo-points li{position:relative;padding-left:30px;color:var(--ink-soft)}
.seo-points li::before{content:"";position:absolute;left:4px;top:10px;width:9px;height:9px;border-radius:3px;background:var(--grad)}
.seo-points strong{color:var(--ink)}

/* ===== Subject view ===== */
.subject-view{max-width:var(--maxw);margin:0 auto;padding:34px 20px 20px;animation:rise .5s both}
.crumbs{font-size:14px;color:var(--ink-mute);margin-bottom:14px;display:flex;gap:8px;align-items:center}
.crumbs a{font-weight:600}
.crumbs a:hover{color:var(--violet)}
.subject-title{font-size:clamp(28px,5vw,42px);letter-spacing:-.02em;margin:0 0 8px}
.subject-desc{color:var(--ink-soft);margin:0 0 24px;max-width:640px}

.toolbar{
  display:flex;align-items:center;justify-content:space-between;gap:14px;flex-wrap:wrap;
  padding:14px 4px;position:sticky;top:66px;z-index:20;
  background:linear-gradient(#fff 70%,rgba(255,255,255,0));
}
.stat{font-size:14.5px;color:var(--ink-mute);font-weight:600}
.stat b{color:var(--ink)}
.btn-expand{
  display:inline-flex;align-items:center;gap:8px;padding:11px 18px;border-radius:12px;
  border:1px solid var(--line-2);background:#fff;color:var(--ink);font-size:14.5px;font-weight:700;
  cursor:pointer;box-shadow:var(--shadow-sm);transition:transform .2s,box-shadow .2s,border-color .2s,color .2s;
}
.btn-expand:hover{transform:translateY(-2px);box-shadow:var(--shadow-md);color:var(--violet);border-color:#c7cdf0}
.btn-expand svg{transition:transform .3s}
.btn-expand[aria-pressed="true"] svg{transform:rotate(180deg)}

/* ===== Task groups & cards ===== */
.task-group{margin:26px 0 0}
.task-group-title{
  display:flex;align-items:center;gap:12px;font-size:15px;font-weight:800;color:var(--ink);
  text-transform:uppercase;letter-spacing:.08em;margin:0 2px 12px;
}
.task-group-title .tg-num{
  display:grid;place-items:center;min-width:30px;height:30px;padding:0 8px;border-radius:9px;
  background:var(--grad-soft);color:var(--violet);font-size:14px;
}
.task-group-title .tg-line{flex:1;height:1px;background:var(--line)}

.q-card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--r-md);
  box-shadow:var(--shadow-sm);margin-bottom:12px;overflow:hidden;
  transition:box-shadow .25s,border-color .25s,transform .25s;
  opacity:0;transform:translateY(10px);animation:rise .5s forwards;
}
.q-card.open{box-shadow:var(--shadow-md);border-color:#dfe3f4}
.q-head{
  display:flex;align-items:center;gap:14px;width:100%;padding:16px 18px;
  background:none;border:0;cursor:pointer;text-align:left;font:inherit;color:inherit;
}
.q-head:hover{background:#fafbff}
.q-badge{
  flex-shrink:0;display:grid;place-items:center;min-width:44px;height:44px;padding:0 10px;border-radius:11px;
  background:var(--grad-soft);color:var(--violet);font-weight:800;font-size:14px;line-height:1.05;text-align:center;
}
.q-titles{flex:1;min-width:0}
.q-name{font-weight:700;font-size:16.5px;letter-spacing:-.01em}
.q-hint{font-size:13.5px;color:var(--ink-mute);font-weight:600;margin-top:1px}
.q-chev{flex-shrink:0;color:var(--ink-mute);transition:transform .3s,color .2s}
.q-card.open .q-chev{transform:rotate(180deg);color:var(--violet)}
.q-head:hover .q-chev{color:var(--violet)}

.q-body{display:grid;grid-template-rows:0fr;transition:grid-template-rows .38s cubic-bezier(.3,.7,.3,1)}
.q-card.open .q-body{grid-template-rows:1fr}
.q-body-inner{overflow:hidden;min-height:0}
.q-content{padding:4px 18px 18px;border-top:1px solid var(--line)}
.q-figure{
  margin:16px 0 0;padding:14px;border-radius:var(--r-sm);background:#fbfbfe;border:1px solid var(--line);
}
.q-figure img{margin:0 auto;border-radius:6px}
.q-figure img + img{margin-top:12px}

/* ===== Answer block ===== */
.answer-wrap{margin-top:16px}
.btn-answer{
  display:inline-flex;align-items:center;gap:9px;padding:11px 20px;border-radius:12px;border:0;cursor:pointer;
  background:var(--grad);color:#fff;font-size:15px;font-weight:700;
  box-shadow:0 8px 20px rgba(99,102,241,.28);transition:transform .2s,box-shadow .2s,filter .2s;
}
.btn-answer:hover{transform:translateY(-2px);box-shadow:0 12px 26px rgba(99,102,241,.36)}
.btn-answer:active{transform:translateY(0)}
.btn-answer .i-eye{display:inline-flex}
.btn-answer.shown{background:#fff;color:var(--ok);border:1px solid var(--ok);box-shadow:none}
.btn-answer.shown:hover{background:var(--ok-bg)}

.answer-panel{display:grid;grid-template-rows:0fr;transition:grid-template-rows .35s ease}
.answer-panel.show{grid-template-rows:1fr;margin-top:14px}
.answer-panel-inner{overflow:hidden;min-height:0}
.answer-box{
  padding:16px 18px;border-radius:var(--r-sm);background:var(--ok-bg);border:1px solid #bfe9cf;
}
.answer-label{display:flex;align-items:center;gap:8px;font-size:13px;font-weight:800;text-transform:uppercase;letter-spacing:.06em;color:var(--ok);margin-bottom:8px}
.answer-values{display:flex;flex-wrap:wrap;gap:8px}
.answer-chip{
  display:inline-block;padding:7px 15px;border-radius:9px;background:#fff;border:1px solid #bfe9cf;
  font-weight:800;font-size:17px;color:#0f7a3d;letter-spacing:.01em;
}
.answer-note{font-size:13.5px;color:var(--ink-soft);margin-top:10px}
.answer-img{margin-top:4px;border-radius:8px;border:1px solid #bfe9cf;background:#fff;overflow:hidden}
.answer-img img{margin:0 auto}
.answer-empty{color:var(--ink-soft);font-size:14.5px}

/* ===== Footer ===== */
.site-footer{margin-top:60px;border-top:1px solid var(--line);background:linear-gradient(#fff,#f7f8fc)}
.footer-inner{max-width:var(--maxw);margin:0 auto;padding:44px 20px}
.footer-brand{font-weight:800;font-size:20px;margin:0 0 10px}
.footer-text{color:var(--ink-soft);max-width:560px;margin:0 0 18px;font-size:15px}
.footer-nav{display:flex;flex-wrap:wrap;gap:8px 18px;margin-bottom:20px}
.footer-nav a{font-size:14.5px;font-weight:600;color:var(--ink-soft)}
.footer-nav a:hover{color:var(--violet)}
.footer-copy{color:var(--ink-mute);font-size:13.5px;margin:0}

/* ===== To top ===== */
.to-top{
  position:fixed;right:22px;bottom:22px;z-index:50;width:48px;height:48px;border-radius:14px;border:0;cursor:pointer;
  background:var(--grad);color:#fff;box-shadow:var(--shadow-lg);display:grid;place-items:center;
  transition:transform .25s,opacity .25s;animation:pop .3s both;
}
.to-top:hover{transform:translateY(-3px)}

/* ===== Animations ===== */
@keyframes rise{from{opacity:0;transform:translateY(18px)}to{opacity:1;transform:translateY(0)}}
@keyframes pop{from{opacity:0;transform:scale(.9)}to{opacity:1;transform:scale(1)}}

/* ===== Responsive ===== */
@media (max-width:860px){
  .subject-cards{grid-template-columns:repeat(2,1fr)}
}
@media (max-width:720px){
  body{font-size:16px}
  .header-inner{height:60px;gap:12px}
  .nav-toggle{display:flex}
  .subject-nav{
    position:absolute;top:60px;left:0;right:0;margin:0;flex-direction:column;gap:2px;
    background:#fff;border-bottom:1px solid var(--line);box-shadow:var(--shadow-md);
    padding:10px 14px 16px;transform:translateY(-12px);opacity:0;pointer-events:none;transition:.25s;
  }
  .subject-nav.open{transform:translateY(0);opacity:1;pointer-events:auto}
  .subject-nav a{padding:13px 15px;font-size:16px}
  .toolbar{top:60px}
  .hero-inner{padding:48px 18px 24px}
  .q-head{padding:14px}
  .q-content{padding:4px 14px 16px}
  .to-top{right:16px;bottom:16px}
}
@media (max-width:480px){
  .subject-cards{grid-template-columns:1fr}
  .q-badge{min-width:40px;height:40px}
  .btn-answer{width:100%;justify-content:center}
}
@media (prefers-reduced-motion:reduce){
  *{animation-duration:.01ms!important;transition-duration:.01ms!important}
  html{scroll-behavior:auto}
  .blob{animation:none}
}