/* Слой — lesson view (student cabinet) */

.lesson-page{
  --side-bg:#1A3E64;
  --sub:#204871;
  --cur:#27527F;
  --player:#0E2640;
  --player-grid:#1B4067;
  --mute-3:#4A6482;
  --hdr:64px;
}
.lesson-page .bare:disabled{cursor:not-allowed}
.lesson-page .btn:disabled{opacity:.4;cursor:not-allowed}
.lesson-page .btn:disabled::before{display:none}
.lesson-page .btn:disabled:hover{color:inherit}
.lesson-page .btn.acc:disabled:hover{color:var(--ink)}
.lesson-page .btn:hover .arr{transform:translateX(3px)}
.mono-s{font-family:var(--f-mono);font-size:11px;letter-spacing:.08em;text-transform:uppercase;color:var(--mute-d)}
.ib{transition:background .3s,color .3s}
.ib:hover{background:var(--line-d)}

/* ---------- app header ---------- */
.app-h{position:sticky;top:0;z-index:40;height:var(--hdr);padding:0 24px;display:flex;align-items:center;gap:20px;border-bottom:1px solid var(--line-d);background:var(--ink)}
.app-h .logo-link{flex-shrink:0}
.app-h-div{width:1px;height:24px;background:var(--line-d);flex-shrink:0}
.prog-toggle{display:none;height:44px;padding:0 12px;border-radius:12px;border:1px solid var(--line-d2);align-items:center;gap:8px;font-size:14px;font-weight:500;flex-shrink:0}
.crumbs{flex-grow:1;min-width:0;display:flex;align-items:center;gap:10px;font-size:14px;color:var(--mute-d);white-space:nowrap}
.crumbs>*{flex-shrink:0}
.crumbs>a{flex-shrink:1;overflow:hidden;text-overflow:ellipsis}
.crumb-cur{color:var(--paper)}
.hprog{display:flex;align-items:center;gap:12px;flex-shrink:0}
.hprog-l{font-family:var(--f-mono);font-size:11px;letter-spacing:.08em;text-transform:uppercase;color:var(--mute-d)}
.hprog-bar{width:180px;height:6px;border-radius:3px;background:var(--line-d);overflow:hidden}
.hprog-bar>span{display:block;height:6px;background:var(--acc);transition:width .6s var(--ease)}
.hprog-v{font-family:var(--f-mono);font-size:13px;min-width:40px}
.bell{position:relative;width:40px;height:40px;border-radius:50%;display:flex;align-items:center;justify-content:center;flex-shrink:0}
.bell-dot{position:absolute;right:9px;top:9px;width:8px;height:8px;border-radius:50%;background:var(--acc)}
.avatar{width:40px;height:40px;border-radius:50%;background:var(--line-d);display:flex;align-items:center;justify-content:center;font-family:var(--f-display);font-size:14px;font-weight:600;flex-shrink:0}

/* ---------- layout ---------- */
.lay{display:grid;grid-template-columns:340px minmax(0,1fr);min-height:calc(100vh - var(--hdr))}
.scrim{display:none}

/* ---------- sidebar ---------- */
.side{position:sticky;top:var(--hdr);height:calc(100vh - var(--hdr));height:calc(100dvh - var(--hdr));background:var(--side-bg);border-right:1px solid var(--line-d);display:flex;flex-direction:column;overflow:hidden}
.side-top{padding:24px 24px 20px;border-bottom:1px solid var(--line-d);display:flex;flex-direction:column;gap:10px}
.side-top-row{display:flex;align-items:center;justify-content:space-between;gap:12px}
.side-close{display:none;width:44px;height:44px;border-radius:12px;align-items:center;justify-content:center;margin:-10px -10px -10px 0}
.side-course{font-family:var(--f-display);font-size:20px;font-weight:600;letter-spacing:-.02em}
.side-sub{font-size:14px;color:var(--mute-d)}
.side-list{flex-grow:1;min-height:0;overflow-y:auto;overscroll-behavior:contain;padding:8px 12px;display:flex;flex-direction:column;gap:2px}

.mod-h{width:100%;min-height:60px;padding:10px 12px;border-radius:12px;display:flex;align-items:center;gap:12px}
.mod-h-t{display:flex;flex-direction:column;gap:4px;flex-grow:1;min-width:0}
.mod-h-n{font-family:var(--f-mono);font-size:11px;letter-spacing:.08em;text-transform:uppercase;color:var(--mute-d)}
.mod-h-title{font-size:15px;font-weight:600;line-height:1.3}
.mod-lock{color:var(--mute-3)}
.mod-h .chev{color:var(--mute-d);transition:transform .5s var(--ease)}
.mod[data-open="true"] .chev{transform:rotate(180deg)}
.row-body{display:grid;grid-template-rows:0fr;transition:grid-template-rows .6s var(--ease)}
.row-body>div{overflow:hidden;min-height:0}
.mod[data-open="true"] .row-body{grid-template-rows:1fr}
.mod[data-open="false"] .row-body>div{visibility:hidden;transition:visibility 0s .6s}
.mod-ls{list-style:none;margin:0;padding:2px 0 10px;display:flex;flex-direction:column;gap:2px}

.ls{width:100%;min-height:46px;padding:8px 12px;border-radius:10px;display:flex;align-items:center;gap:12px;transition:background .3s}
.ls:hover:not(:disabled){background:var(--sub)}
.ls[data-cur="true"]{background:var(--cur)}
.ls[data-cur="true"] .lt{color:var(--paper);font-weight:600}
.ls-st{display:flex;flex-shrink:0}
.st{width:22px;height:22px;border-radius:50%;display:flex;align-items:center;justify-content:center;flex-shrink:0}
.st-done{background:var(--line-d2);color:var(--paper)}
.st-done .ico{stroke-width:2.4}
.st-cur{background:var(--acc);color:var(--ink)}
.st-cur .ico{fill:currentColor}
.st-todo{border:1.5px solid var(--mute-3)}
.st-lock{color:var(--mute-3)}
.lt{flex-grow:1;font-size:14px;line-height:1.35;color:var(--mute-d2)}
.ls-n{font-family:var(--f-mono);font-size:11px;color:var(--mute-d)}

.chat{margin:12px;padding:16px;border-radius:16px;background:var(--sub);border:1px solid var(--line-d);display:flex;align-items:center;gap:12px;flex-shrink:0}
.chat-ic{width:40px;height:40px;border-radius:12px;background:var(--acc);color:var(--ink);display:flex;align-items:center;justify-content:center;flex-shrink:0}
.chat-t{display:flex;flex-direction:column;gap:2px;flex-grow:1}
.chat-t1{font-size:14px;font-weight:600}
.chat-t2{font-size:13px;color:var(--mute-d)}
.chat-go{color:var(--mute-d)}

/* ---------- main ---------- */
.main{min-width:0;width:100%;max-width:1360px;padding:24px 40px 32px;display:flex;flex-direction:column;gap:24px}

/* player */
.player{position:relative;aspect-ratio:16/9;flex-shrink:0;border-radius:22px;overflow:hidden;background:var(--player);border:1px solid var(--line-d);color:var(--acc);display:flex;align-items:center;justify-content:center;background-image:linear-gradient(var(--player-grid) 1px,transparent 1px),linear-gradient(90deg,var(--player-grid) 1px,transparent 1px);background-size:32px 32px}
.player:fullscreen{border-radius:0;border:0}
.player .ill{width:59%;max-width:600px;height:auto;aspect-ratio:3/2;stroke-width:1.2}
.player .ill .th{stroke-width:.8;opacity:.55}
.player .ill .dw{animation:draw 3.2s cubic-bezier(.65,0,.35,1) infinite alternate backwards}
.player .ill>.dw:nth-child(2){animation-delay:0s}
.player .ill>.dw:nth-child(3){animation-delay:.1s}
.player .ill>.dw:nth-child(4){animation-delay:.2s}
.player .ill>.dw:nth-child(5){animation-delay:.3s}
.player .ill>.dw:nth-child(6){animation-delay:.4s}
.player .ill>.dw:nth-child(7){animation-delay:.5s}
.player .ill>.dw:nth-child(8){animation-delay:.6s}
.player .ill>.dw:nth-child(9){animation-delay:.7s}
.player .ill>.dw:nth-child(10){animation-delay:.8s}
.player .ill>.dw:nth-child(11){animation-delay:.9s}
.player.paused .ill .dw{animation:none}

.pchip{position:absolute;top:18px;height:30px;padding:0 12px;border-radius:999px;background:rgba(22,56,92,.85);border:1px solid var(--line-d);color:var(--paper);display:flex;align-items:center;font-family:var(--f-mono);font-size:11px}
.pchip-l{left:20px;letter-spacing:.08em;text-transform:uppercase}
.pchip-r{right:20px}

.bigplay{position:absolute;left:50%;top:50%;width:104px;height:104px;margin:-52px 0 0 -52px;border-radius:50%;background:var(--acc);color:var(--ink);display:flex;align-items:center;justify-content:center;transition:transform .5s var(--ease)}
.bigplay:hover{transform:scale(1.08)}
.bigplay .ico{fill:currentColor;margin-left:4px}
.ring{animation:ring 2s ease-out infinite}
.player.playing .bigplay{display:none}

.pbar{position:absolute;left:16px;right:16px;bottom:16px;height:60px;padding:0 12px;border-radius:16px;background:rgba(22,56,92,.9);border:1px solid var(--line-d);color:var(--paper);display:flex;align-items:center;gap:16px}
.pplay{width:40px;height:40px;border-radius:50%;background:var(--paper);color:var(--ink);display:flex;align-items:center;justify-content:center;flex-shrink:0}
.pplay .ic-play{fill:currentColor;margin-left:2px}
.pplay .ic-pause{stroke-width:3;display:none}
.player.playing .pplay .ic-play{display:none}
.player.playing .pplay .ic-pause{display:block}
.ptime{font-family:var(--f-mono);font-size:13px;color:var(--mute-d2);white-space:nowrap}
.tl{position:relative;flex-grow:1;min-width:40px;height:4px;border-radius:2px;background:var(--line-d2)}
.tl-fill{position:relative;display:block;width:34%;height:4px;border-radius:2px;background:var(--acc)}
.tl-fill::after{content:"";position:absolute;right:-7px;top:-5px;width:14px;height:14px;border-radius:50%;background:var(--paper);transition:transform .3s}
.tl:hover .tl-fill::after{transform:scale(1.3)}
.player.playing .tl-fill{animation:play 40s linear forwards}
.tl-mk{position:absolute;top:0;width:3px;height:4px;background:var(--ink)}
.pb-speed{height:36px;padding:0 10px;border-radius:8px;font-family:var(--f-mono);font-size:13px;flex-shrink:0}
.pb-sq{width:36px;height:36px;border-radius:8px;display:flex;align-items:center;justify-content:center;flex-shrink:0}

/* title row */
.ltitle{display:flex;align-items:flex-end;justify-content:space-between;gap:32px}
.ltitle-t{display:flex;flex-direction:column;gap:10px;min-width:0}
.ltitle-eb{font-family:var(--f-mono);font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:var(--mute-d)}
.ltitle h1{font-family:var(--f-display);font-size:32px;font-weight:600;line-height:1.15;letter-spacing:-.03em;overflow-wrap:anywhere}
.ltitle-nav{display:flex;gap:10px;flex-shrink:0}
.btn.nb{height:52px;padding:0 22px;font-size:15px;font-weight:600;gap:8px}
.btn.ghost.nb{color:var(--paper)}
.btn.ghost.nb:hover{color:var(--ink)}
.btn.s44{height:44px;padding:0 20px;font-size:14px;font-weight:600}

/* tabs */
.tabs-row{display:flex;align-items:center;justify-content:space-between;gap:24px;border-bottom:1px solid var(--line-d)}
.tabs{display:flex;gap:32px;min-width:0}
.tab{position:relative;height:48px;font-size:15px;font-weight:500;color:var(--mute-d);white-space:nowrap;flex-shrink:0;transition:color .3s}
.tab::after{content:"";position:absolute;left:0;right:0;bottom:-1px;height:2px;background:var(--acc);transform:scaleX(0);transform-origin:left center;transition:transform .5s var(--ease)}
.tab[data-active="true"]{color:var(--paper)}
.tab[data-active="true"]::after{transform:scaleX(1)}
.tab:hover{color:var(--paper)}
.tab:focus-visible{outline-offset:-2px}
.done-t{display:flex;align-items:center;gap:12px;min-height:44px;font-size:14px;color:var(--mute-d2);white-space:nowrap;flex-shrink:0}
.sw{position:relative;width:44px;height:24px;border-radius:999px;background:var(--line-d2);display:block;transition:background .3s}
.sw .knob{position:absolute;left:2px;top:2px;width:20px;height:20px;border-radius:50%;background:var(--paper);display:block;transition:transform .45s var(--ease)}
.done-t[aria-pressed="true"] .sw{background:var(--acc)}
.done-t[aria-pressed="true"] .knob{transform:translateX(20px)}

/* panes */
.pane{animation:paneIn .6s var(--ease) backwards}
.pane[hidden]{display:none!important}
.pane:focus-visible{outline:2px solid var(--acc);outline-offset:6px;border-radius:4px}
.pane-desc{display:grid;grid-template-columns:minmax(0,1fr) 380px;gap:48px}
.desc-t{display:flex;flex-direction:column;gap:14px}
.desc-p1{font-size:17px;line-height:1.6;color:var(--mute-d2)}
.desc-p2{font-size:15px;line-height:1.6;color:var(--mute-d)}
.chap{list-style:none;margin:0;padding:0;display:flex;flex-direction:column}
.chap li{min-height:40px;padding:8px 0;display:flex;align-items:center;gap:16px;border-bottom:1px solid var(--line-d);font-size:14px}
.chap li:last-child{border-bottom:0}
.chap li>span{width:44px;flex-shrink:0;font-family:var(--f-mono);color:var(--acc)}

.pane-files{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}
.file{padding:20px;border-radius:16px;border:1px solid var(--line-d);display:flex;align-items:center;gap:14px;transition:background .3s,border-color .3s}
.file:hover{background:var(--sub);border-color:var(--line-d2)}
.file-ext{width:48px;height:48px;border-radius:12px;background:var(--sub);color:var(--acc);display:flex;align-items:center;justify-content:center;flex-shrink:0;font-family:var(--f-mono);font-size:11px;font-weight:500}
.file-t{flex-grow:1;min-width:0;display:flex;flex-direction:column;gap:2px}
.file-t1{font-size:15px;font-weight:600}
.file-t2{font-size:13px;color:var(--mute-d)}

.pane-hw{display:grid;grid-template-columns:minmax(0,1fr) 420px;gap:32px}
.hw-t{display:flex;flex-direction:column;gap:12px}
.hw-h{font-family:var(--f-body);font-size:18px;font-weight:600;line-height:1.3}
.hw-p{font-size:16px;line-height:1.6;color:var(--mute-d2)}
.hw-due,.qa-l .mono-s{font-size:12px}
.dz{padding:24px;border-radius:18px;border:1.5px dashed var(--line-d2);display:flex;flex-direction:column;align-items:center;justify-content:center;gap:12px;text-align:center;transition:border-color .3s,background .3s}
.dz:hover,.dz.drag{border-color:var(--acc);background:#1D436B}
.dz-ic{color:var(--acc)}
.dz-t{font-size:15px}
.dz-files{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:4px;font-family:var(--f-mono);font-size:12px;color:var(--mute-d2);max-width:100%}
.dz-files li{overflow-wrap:anywhere}
.form-msg{font-size:14px;line-height:1.5;color:var(--mute-d2)}
.form-msg:empty{display:none}
.form-msg.ok{color:var(--paper)}
.form-msg.ok::before{content:"";display:inline-block;width:8px;height:8px;border-radius:50%;background:var(--acc);margin-right:8px;vertical-align:1px}
.form-msg.err{color:var(--acc)}

.qa{display:flex;flex-direction:column;gap:14px}
.qa-l{display:flex;flex-direction:column;gap:8px}
.qa textarea{width:100%;padding:16px;border-radius:16px;border:1px solid var(--line-d2);background:var(--side-bg);color:var(--paper);font:inherit;font-size:16px;resize:none}
.qa textarea::placeholder{color:var(--mute-d)}
.qa-f{display:flex;justify-content:space-between;align-items:center;gap:16px}
.qa-note{font-size:14px;color:var(--mute-d)}

@keyframes play{from{width:34%}to{width:100%}}
@keyframes ring{0%{box-shadow:0 0 0 0 var(--acc)}100%{box-shadow:0 0 0 28px transparent}}
@keyframes paneIn{from{opacity:0;transform:translateY(16px)}to{opacity:1;transform:none}}

/* ---------- ≤1200: tighten ---------- */
@media (max-width:1200px){
  .lay{grid-template-columns:300px minmax(0,1fr)}
  .main{padding:24px 32px 32px}
  .pane-desc{grid-template-columns:minmax(0,1fr) 320px;gap:32px}
  .pane-hw{grid-template-columns:minmax(0,1fr) 340px}
  .hprog-l{display:none}
}

/* ---------- ≤1024: sidebar → off-canvas drawer ---------- */
@media (max-width:1024px){
  .app-h{gap:16px}
  .prog-toggle{display:flex}
  .hprog-bar{width:120px}
  .lay{grid-template-columns:minmax(0,1fr)}
  .side{position:fixed;left:0;top:0;bottom:0;z-index:60;width:min(360px,88vw);height:100%;border-right:1px solid var(--line-d);transform:translateX(-100%);visibility:hidden;transition:transform .5s var(--ease),visibility 0s .5s}
  .side[data-open="true"]{transform:none;visibility:visible;transition:transform .5s var(--ease),visibility 0s 0s}
  .side-close{display:flex}
  .scrim{display:block;position:fixed;inset:0;z-index:55;background:rgba(14,38,64,.7);opacity:0;transition:opacity .4s}
  .scrim[hidden]{display:none}
  .scrim[data-on="true"]{opacity:1}
  .main{max-width:none;padding:24px 32px 40px}
  .ltitle{flex-wrap:wrap;align-items:flex-start;row-gap:20px}
  .pane-desc,.pane-hw{grid-template-columns:minmax(0,1fr)}
  .pane-files{grid-template-columns:repeat(2,minmax(0,1fr))}
  .pb-sq,.bell{width:44px;height:44px}
  .pb-speed{height:44px}
}

/* ---------- ≤640: phone ---------- */
@media (max-width:640px){
  .app-h{padding:0 16px;gap:10px}
  .app-h-div,.crumbs{display:none}
  .prog-toggle{width:44px;padding:0;justify-content:center}
  .prog-toggle-t{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}
  .hprog{margin-left:auto;gap:8px}
  .hprog-bar{width:56px}
  .hprog-v{min-width:0}
  .avatar{width:44px;height:44px}
  .main{padding:16px 16px 40px;gap:20px}

  .player{border-radius:16px}
  .player .ill{width:64%}
  .pchip{top:10px;height:26px;padding:0 10px;font-size:10px}
  .pchip-l{left:10px}
  .pchip-r{right:10px}
  .bigplay{width:60px;height:60px;margin:-30px 0 0 -30px}
  .bigplay .ico{width:24px;height:24px;margin-left:3px}
  .pbar{left:8px;right:8px;bottom:8px;height:52px;padding:0 4px 0 6px;gap:10px;border-radius:12px}
  .pplay{width:44px;height:44px}
  .ptime{font-size:11px}
  .pb-opt{display:none}

  .ltitle h1{font-size:24px}
  .ltitle-nav{width:100%}
  .ltitle-nav .btn{flex:1 1 0;height:48px;padding:0 14px;min-width:0;font-size:14px}

  .tabs-row{flex-direction:column;align-items:stretch;gap:8px;border-bottom:0}
  .tabs{gap:24px;overflow-x:auto;scrollbar-width:none;border-bottom:1px solid var(--line-d);margin:0 -16px;padding:0 16px;scroll-padding:0 16px}
  .tabs::-webkit-scrollbar{display:none}
  .tab::after{bottom:0}
  .done-t{justify-content:space-between}

  .desc-p1{font-size:16px}
  .pane-files{grid-template-columns:minmax(0,1fr)}
  .file{padding:16px}
  .qa-f{flex-direction:column;align-items:stretch}
  .qa-f .btn{width:100%}
  .dz .btn{width:100%}
}
@media (max-width:360px){
  .ltitle-nav{flex-direction:column}
}

@media (prefers-reduced-motion:reduce){
  .side{transition:none}
}

/* real video (uploaded file or embed) instead of the illustrated placeholder */
.player--video{background:#000;background-image:none}
.player--video video,.player--video iframe{position:absolute;inset:0;width:100%;height:100%;border:0;background:#000}