:root {
  /* KBTI brand — same theme as kbti.cloud / the SDLC app */
  --red: #a11c1c;
  --red-hover: #c42222;
  --red-deep: #8b1616;
  --red-soft: #faeded;
  --navy: #1a1a2e;
  --navy-2: #16213e;
  --bg: #f7f6f5;
  --card: #ffffff;
  --ink: #1a1a2e;
  --muted: #6b6b7b;
  --line: #e7e2e2;
  --line-strong: #d3cccc;
  --ok: #15803d;
  --ok-soft: #dcfce7;
  --warn: #b45309;
  --radius: 14px;
  --radius-sm: 10px;
  --shadow-sm: 0 1px 2px rgba(26,26,46,.05);
  --shadow-md: 0 4px 14px rgba(26,26,46,.09);
  --shadow-lg: 0 12px 32px rgba(26,26,46,.14);
  --sp: 4px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
  display: flex;
  min-height: 100vh;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

:focus-visible { outline: 2px solid var(--red); outline-offset: 2px; border-radius: 4px; }

.wrap { width: 100%; max-width: 1080px; margin: 0 auto; padding: 26px 20px 48px; flex: 1; }

h1 { font-size: 1.65rem; letter-spacing: -.015em; line-height: 1.25; margin: 0 0 8px; }
h2 { font-size: 1.1rem; margin: 0 0 12px; letter-spacing: -.01em; }
a { color: var(--red); }
code { background: var(--red-soft); border-radius: 5px; padding: 1px 6px; font-size: .88em; }

/* ---------- top bar ---------- */
.topbar {
  background: var(--red);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 22px;
  position: sticky;
  top: 0;
  z-index: 20;
  box-shadow: 0 4px 12px rgba(26, 26, 46, 0.18);
}
.brand-href { display: flex; align-items: center; gap: 10px; color: #fff; text-decoration: none; }
.logo { width: 28px; height: 28px; display: block; }
.brand-name { font-weight: 700; font-size: 16px; }
.brand-name em { font-style: normal; color: #ffd9d9; font-weight: 500; }

.nav { display: flex; align-items: center; gap: 14px; flex-wrap: wrap; }
.nav-link { color: #ffe3e3; text-decoration: none; font-weight: 600; }
.nav-link:hover { color: #fff; text-decoration: underline; }

.search input {
  font: inherit; font-size: .9rem;
  background: rgba(255,255,255,.14);
  border: 1px solid rgba(255,255,255,.28);
  color: #fff;
  border-radius: 999px; padding: 7px 16px 7px 34px;
  width: 240px; max-width: 46vw;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='14' height='14' viewBox='0 0 24 24' fill='none' stroke='%23ffd9d9' stroke-width='2.4' stroke-linecap='round'%3E%3Ccircle cx='11' cy='11' r='7'/%3E%3Cpath d='m20 20-3.2-3.2'/%3E%3C/svg%3E");
  background-repeat: no-repeat; background-position: 12px center;
  transition: background-color .15s, border-color .15s;
}
.search input::placeholder { color: #f2caca; }
.search input:focus { background-color: rgba(255,255,255,.22); border-color: rgba(255,255,255,.5); outline: none; }

/* ---------- hero (landing) ---------- */
.hero {
  position: relative;
  background: var(--red);           /* KBTI brand red — solid, no gradients */
  border-radius: 18px;
  padding: 48px 44px 44px;
  margin-bottom: 30px;
  color: #fff;
  overflow: hidden;
  box-shadow: var(--shadow-md);
}
.hero-inner { position: relative; z-index: 1; max-width: 720px; }
.hero-eyebrow {
  display: inline-flex; align-items: center; gap: 9px;
  font-size: .78rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase;
  color: #fff; background: rgba(255,255,255,.08);
  border: 1px solid rgba(255,255,255,.16);
  border-radius: 999px; padding: 6px 14px; margin-bottom: 20px;
}
.hero-logo { width: 16px; height: 16px; display: block; }
.hero-title {
  font-size: clamp(2rem, 5.2vw, 3.1rem);
  line-height: 1.08; letter-spacing: -.025em; margin: 0 0 14px; color: #fff;
}
.hero-title em { font-style: normal; color: #fff; }
.hero-sub { color: #fff; margin: 0 0 22px; font-size: 1.14rem; max-width: 58ch; }
.hero-sub strong { color: #fff; }
.hero-stats {
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
  color: #fff; font-size: .86rem;
}
.hero-stats strong { color: #fff; font-size: 1rem; }
.hero-stats .dot { width: 4px; height: 4px; border-radius: 50%; background: rgba(255,255,255,.6); }

/* flat inline icons */
.ic { width: 14px; height: 14px; vertical-align: -2px; flex: none; }
.card-meta li { display: inline-flex; align-items: center; gap: 5px; }

/* generic sub (reused on course page) */
.panel .hero-sub, .page-head .hero-sub { color: var(--muted); }

/* ---------- course cards ---------- */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(270px, 1fr));
  gap: 18px;
}
.card {
  --accent: var(--red);
  display: flex; flex-direction: column;
  background: var(--card);
  border-radius: var(--radius);
  overflow: hidden;
  text-decoration: none;
  color: var(--ink);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--line);
  transition: transform .16s ease, box-shadow .16s ease, border-color .16s ease;
  position: relative;
}
.card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--line-strong); }
.card-band { height: 6px; background: var(--accent); flex: none; }
.card-body { padding: 18px 18px 14px; display: flex; flex-direction: column; flex: 1; gap: 8px; }
.card-top { display: flex; gap: 6px; flex-wrap: wrap; }
.card-title { margin: 0; font-size: 1.05rem; line-height: 1.35; }
.card-summary {
  margin: 0; color: var(--muted); font-size: .88rem;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}
.card-meta { list-style: none; display: flex; flex-wrap: wrap; gap: 12px; margin: 0; padding: 0; color: var(--muted); font-size: .8rem; }
.card-foot { display: flex; justify-content: space-between; align-items: center; gap: 8px; margin-top: auto; padding-top: 6px; }
.card-audience { margin-top: 0; padding-top: 0; font-size: 12px; color: var(--navy-2); font-weight: 600;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.card-resume { font-size: .78rem; font-weight: 700; color: var(--red); white-space: nowrap; }
.card-progress { padding-top: 4px; }
.card-progress .bar { display: block; height: 4px; border-radius: 999px; background: var(--line); overflow: hidden; }
.card-progress .fill { display: block; height: 100%; width: 0; border-radius: 999px;
  background: var(--red); transition: width .5s ease; }

.pill { background: var(--red-soft); color: var(--red); font-size: 12px; font-weight: 700; border-radius: 999px; padding: 3px 10px; }
.pill-lang { background: #ececf2; color: var(--navy-2); }
.tag { background: #ececf2; color: var(--navy-2); font-size: 11px; font-weight: 600; border-radius: 6px; padding: 2px 8px; }
.tag-quiz { background: #fdeaea; color: var(--red); }

/* ---------- empty state ---------- */
.empty-state {
  grid-column: 1 / -1;
  text-align: center; padding: 56px 20px;
  background: var(--card); border: 1px dashed var(--line-strong); border-radius: var(--radius);
}
.empty-state .empty-logo { width: 44px; opacity: .8; }
.empty-state h2 { margin: 12px 0 4px; }
.empty-state p { color: var(--muted); margin: 0; }
.empty { color: var(--muted); }

/* ---------- crumbs ---------- */
.crumbs { font-size: .84rem; color: var(--muted); margin-bottom: 14px; }
.crumbs a { color: var(--red); text-decoration: none; font-weight: 600; }
.crumbs a:hover { text-decoration: underline; }
.crumb-sep { margin: 0 6px; color: var(--line-strong); }

/* ---------- course page ---------- */
.page-head {
  background: var(--card);
  border: 1px solid var(--line);
  border-top: 5px solid var(--accent, var(--red));
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 26px 28px;
  margin-bottom: 22px;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 26px;
  align-items: start;
}
.head-top { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 10px; }
.head-main .hero-sub { margin: 4px 0 12px; }
.stat-row { list-style: none; display: flex; flex-wrap: wrap; gap: 16px; margin: 0 0 16px; padding: 0; color: var(--muted); font-size: .88rem; }
.stat-row strong { color: var(--ink); font-size: 1rem; }
.cta-row { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
.progress-inline { display: flex; align-items: center; gap: 10px; color: var(--muted); font-size: .84rem; font-weight: 600; }
.ring { width: 34px; height: 34px; transform: rotate(-90deg); }
.ring circle { fill: none; stroke-width: 4.5; }
.ring-bg { stroke: var(--line); }
.ring-fg { stroke: var(--red); stroke-linecap: round; stroke-dasharray: 97.4; stroke-dashoffset: 97.4; transition: stroke-dashoffset .6s ease; }

.head-cover {
  max-width: 300px; background: var(--bg);
  border: 1px solid var(--line); border-radius: var(--radius-sm);
  padding: 14px 16px; font-size: .9rem;
}
.head-cover .cover-label { font-size: 11px; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); font-weight: 700; }
.cover-body p { margin: 6px 0 0; }
.cover-body h1, .cover-body h2 { font-size: .95rem; margin: 6px 0 2px; }

.course-grid { display: grid; grid-template-columns: 1fr 380px; gap: 22px; align-items: start; }
.course-toc { position: sticky; top: 76px; }
.course-toc .panel { margin: 0; }

.panel {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 20px 22px;
  margin-bottom: 20px;
}
.panel-row { display: flex; align-items: baseline; justify-content: space-between; gap: 10px; }

/* ---------- lesson list (TOC) ---------- */
.lesson-list { list-style: none; margin: 0; padding: 0; }
.lesson-item + .lesson-item { border-top: 1px solid var(--line); }
.lesson-link {
  display: flex; align-items: center; gap: 12px;
  padding: 11px 8px; text-decoration: none; color: var(--ink);
  border-radius: var(--radius-sm); transition: background .12s;
}
.lesson-link:hover { background: var(--bg); }
.lesson-num {
  flex: none; width: 26px; height: 26px; border-radius: 50%;
  background: var(--red-soft); color: var(--red);
  font-size: 12px; font-weight: 700;
  display: inline-flex; align-items: center; justify-content: center;
  transition: background .2s, color .2s;
}
.lesson-main { display: flex; flex-direction: column; gap: 3px; min-width: 0; }
.lesson-title { font-weight: 600; font-size: .92rem; line-height: 1.3; }
.lesson-tags { display: flex; gap: 5px; flex-wrap: wrap; }
.lesson-state { margin-left: auto; flex: none; width: 20px; height: 20px; border-radius: 50%;
  border: 2px solid var(--line-strong); position: relative; transition: all .25s; }
.lesson-item.done .lesson-state { background: var(--ok); border-color: var(--ok); }
.lesson-item.done .lesson-state::after {
  content: ""; position: absolute; left: 5px; top: 2px; width: 6px; height: 10px;
  border: solid #fff; border-width: 0 2px 2px 0; transform: rotate(42deg);
}
.lesson-item.done .lesson-num { background: var(--ok); color: #fff; }
.lesson-item.done .lesson-title { color: var(--muted); }

/* ---------- lesson page (app shell: sidebar + framed content) ---------- */
/* App shell: the BODY is a flex column (topbar + fill), so no hardcoded
   topbar heights — the frame and the prev/next bar always fit the viewport. */
body.lesson-page { overflow: hidden; height: 100dvh; display: flex; flex-direction: column; }
body.lesson-page .topbar { flex: none; }
body.lesson-page .foot { display: none; }
body.lesson-page .wrap { flex: 1; min-height: 0; overflow: hidden;
  max-width: none; padding: 0; margin: 0; width: 100%; }

.lesson-shell {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  grid-template-rows: minmax(0, 1fr);
  height: 100%;
}

/* sidebar */
.lesson-side {
  border-right: 1px solid var(--line);
  background: var(--card);
  overflow-y: auto;
  padding: 16px 12px 24px;
}
.side-course { display: flex; flex-direction: column; gap: 2px; text-decoration: none;
  padding: 10px 10px 12px; border-bottom: 1px solid var(--line); margin-bottom: 10px; }
.side-course-title { color: var(--ink); font-weight: 700; font-size: .95rem; line-height: 1.3; }
.side-course-meta { color: var(--muted); font-size: .78rem; }
.side-list .lesson-link { padding: 10px 10px; border-radius: var(--radius-sm); }
.side-list .lesson-item.active .lesson-link { background: var(--red-soft); }
.side-list .lesson-item.active .lesson-num { background: var(--red); color: #fff; }
.side-list .lesson-item.active .lesson-title { color: var(--red); }

.side-toggle { display: none; }

/* main column */
.lesson-main { display: flex; flex-direction: column; min-width: 0; min-height: 0; height: 100%; }
/* grid items default to min-height:auto — without min-height:0 the main
   column refuses to shrink below content height, the frame never
   constrains, and the navbar falls below the locked viewport. */
.lesson-head { flex: none; }
.deck-nav { flex: none; }

.lesson-head {
  display: flex; align-items: center; justify-content: space-between; gap: 18px;
  padding: 14px 26px;
  border-bottom: 1px solid var(--line);
  background: var(--card);
}
.lesson-head-info h1 { font-size: 1.15rem; margin: 4px 0 0; }
.lesson-head-actions { display: flex; align-items: center; gap: 18px; flex-wrap: wrap; }

.lesson-progress { display: flex; align-items: center; gap: 10px; }
.lp-bar { width: 130px; height: 5px; border-radius: 999px; background: var(--line); overflow: hidden; }
.lp-fill { display: block; height: 100%; width: 0; border-radius: 999px;
  background: var(--red); transition: width .5s ease; }
.lp-txt { font-size: .78rem; color: var(--muted); font-weight: 600; white-space: nowrap; }

/* the frame: each lesson page fills the viewport, no scrolling between pages */
.lesson-frame { flex: 1; min-height: 0; padding: 20px 26px; background: var(--bg); }
.lesson-scroll {
  position: relative; height: 100%; overflow: hidden;
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  max-width: 900px; margin: 0 auto;
}
.deck-page {
  position: absolute; inset: 0;
  display: flex; flex-direction: column;
  overflow-y: auto; scrollbar-width: thin;
  padding: clamp(24px, 5vh, 48px) clamp(28px, 6vw, 64px);
  opacity: 0; visibility: hidden;
  transition: opacity .45s ease, visibility .45s;
}
.deck-page.active { opacity: 1; visibility: visible; z-index: 1; }
.deck-page .lesson-body { margin: auto; width: 100%; }
.deck-page .lesson-body > :first-child { margin-top: 0; }
.deck-page .lesson-body > :last-child { margin-bottom: 0; }
.deck-page.quiz-page .quiz { margin: auto; width: 100%; }
.lesson-body { font-size: 1.02rem; line-height: 1.75; max-width: 74ch; margin: 0 auto; }
.lesson-body h1, .lesson-body h2 { border-bottom: 1px solid var(--line); padding-bottom: 6px; margin-top: 28px; }
.lesson-body h1 { font-size: 1.3rem; }
.lesson-body h2 { font-size: 1.12rem; }
.lesson-body h3 { font-size: 1rem; margin-top: 22px; }
.lesson-body table { width: 100%; border-collapse: collapse; font-size: .92rem; }
.lesson-body th, .lesson-body td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; }
.lesson-body th { background: var(--bg); }
.lesson-body pre { background: var(--navy-2); color: #e8e8f2; border-radius: var(--radius-sm);
  padding: 14px 16px; overflow-x: auto; font-size: .86rem; }
.lesson-body pre code { background: none; color: inherit; padding: 0; }
.lesson-body blockquote { border-left: 4px solid var(--red); background: var(--red-soft);
  margin: 14px 0; padding: 10px 16px; border-radius: 0 var(--radius-sm) var(--radius-sm) 0; }
.lesson-body img { max-width: 100%; border-radius: var(--radius-sm); }
.lesson-body .mermaid { text-align: center; margin: 18px 0; overflow-x: auto; }
.lesson-body .mermaid svg { max-width: 100%; height: auto; }

/* quiz rides inside the frame */
.quiz { max-width: 74ch; margin: 26px auto 6px; padding-top: 22px; border-top: 1px solid var(--line); }

/* deck navigation: page dots/arrows/counter (sidebar handles jumping between lessons) */
.deck-nav {
  flex: none;
  display: flex; align-items: center; justify-content: center; gap: 18px;
  padding: 10px 26px 12px;
  border-top: 1px solid var(--line);
  background: var(--card);
}
.deck-arrow {
  width: 40px; height: 40px; border-radius: 50%;
  border: 1px solid var(--line-strong); background: var(--card); color: var(--muted);
  font-size: 18px; line-height: 1; cursor: pointer; padding: 0;
  display: inline-flex; align-items: center; justify-content: center;
  transition: background .15s, border-color .15s, color .15s;
}
.deck-arrow:hover:not(:disabled) { border-color: var(--red); color: var(--red); background: var(--red-soft); }
.deck-arrow:disabled { opacity: .28; cursor: default; }
.deck-dots { display: flex; align-items: center; gap: 8px; }
.deck-dot {
  width: 9px; height: 9px; border-radius: 999px; padding: 0; border: none;
  background: rgba(26,26,46,.14); cursor: pointer;
  transition: width .25s ease, background .25s ease;
}
.deck-dot.active { width: 26px; background: var(--red); }
.deck-dot:hover:not(.active) { background: rgba(26,26,46,.26); }
.deck-counter {
  font-size: .78rem; color: var(--muted); font-weight: 600;
  font-variant-numeric: tabular-nums; min-width: 84px; text-align: center;
}

/* landscape monitors: roomier pages, slightly larger type */
@media (orientation: landscape) and (min-width: 700px) {
  .deck-page { padding: clamp(28px, 6vh, 56px) clamp(48px, 7vw, 90px); }
  .deck-page .lesson-body { font-size: 1.06rem; }
}

/* responsive: sidebar becomes a drawer */
@media (max-width: 900px) {
  .lesson-shell { grid-template-columns: 1fr; }
  .lesson-side {
    position: fixed; z-index: 40; top: 53px; bottom: 0; left: 0; width: min(320px, 84vw);
    transform: translateX(-102%); transition: transform .22s ease;
    box-shadow: var(--shadow-lg);
  }
  .lesson-side.open { transform: none; }
  .side-toggle {
    display: inline-flex; align-items: center; gap: 8px;
    position: fixed; z-index: 41; bottom: 86px; left: 14px;
    background: var(--red); color: #fff; border: none; border-radius: 999px;
    font: inherit; font-weight: 700; font-size: .82rem;
    padding: 10px 16px; box-shadow: var(--shadow-lg); cursor: pointer;
  }
  .lesson-head { padding: 12px 16px; }
  .lesson-head-info h1 { font-size: 1.02rem; }
  .lesson-frame { padding: 12px 12px; }
  .deck-page { padding: 20px 18px 26px; }
  .deck-nav { padding: 8px 10px 10px; gap: 12px; }
  .deck-counter { min-width: 72px; }
  .lp-bar { width: 84px; }
}

/* ---------- quiz ---------- */
.quiz { max-width: 74ch; margin: 0 auto 22px; }
.quiz-question { margin-bottom: 18px; }
.quiz-question h3 { margin: 0 0 10px; font-size: 1rem; }
.quiz-option {
  display: flex; align-items: center; gap: 12px;
  border: 1.5px solid var(--line); border-radius: var(--radius-sm);
  padding: 12px 14px; margin-bottom: 8px; cursor: pointer;
  font-size: .95rem; background: var(--card);
  transition: border-color .12s, background .12s, transform .06s;
  min-height: 44px;
}
.quiz-option:hover { border-color: var(--red); }
.quiz-option:active { transform: scale(.995); }
.quiz-option > span:first-child {
  flex: none; width: 26px; height: 26px; border-radius: 50%;
  border: 1.5px solid var(--line-strong);
  display: inline-flex; align-items: center; justify-content: center;
  font-size: 12px; font-weight: 700; color: var(--muted);
  transition: all .15s;
}
.quiz-option.selected { border-color: var(--red); background: var(--red-soft); }
.quiz-option.selected > span:first-child { background: var(--red); border-color: var(--red); color: #fff; }
.quiz-option.correct { border-color: var(--ok); background: var(--ok-soft); }
.quiz-option.correct > span:first-child { background: var(--ok); border-color: var(--ok); color: #fff; }
.quiz-option.wrong { border-color: #ef4444; background: #fdecec; }
.quiz-explain { margin: 8px 0 0; font-size: .88rem; color: var(--muted);
  background: var(--bg); border-radius: var(--radius-sm); padding: 10px 14px; }
.quiz-actions { display: flex; gap: 10px; margin-top: 14px; }
.quiz-result { margin-top: 14px; padding: 14px 18px; border-radius: var(--radius-sm); font-weight: 700; }
.quiz-result.pass { background: var(--ok-soft); color: var(--ok); border: 1px solid #a7dfb8; }
.quiz-result.fail { background: #fdf3e7; color: var(--warn); border: 1px solid #f3d9ae; }

/* ---------- buttons ---------- */
.btn {
  font: inherit; font-weight: 600; text-decoration: none; cursor: pointer;
  border: 1.5px solid var(--line-strong); background: var(--card); color: var(--ink);
  border-radius: var(--radius-sm); padding: 9px 18px;
  transition: background .14s, border-color .14s, transform .05s;
  display: inline-flex; align-items: center; gap: 8px; min-height: 40px;
}
.btn:hover { border-color: var(--navy-2); background: var(--bg); }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--red); border-color: var(--red); color: #fff; }
.btn-primary:hover { background: var(--red-hover); border-color: var(--red-hover); }
.btn-lg { padding: 12px 24px; font-size: 1rem; border-radius: 999px; min-height: 46px; }
.btn-complete { border-radius: 999px; }
.btn-complete.done { background: var(--ok); border-color: var(--ok); color: #fff; }
.btn:disabled { opacity: .5; cursor: not-allowed; }

/* ---------- search results ---------- */
.search-results { margin-bottom: 20px; display: grid; gap: 10px; }
.search-results .card { padding: 14px 18px; font-weight: 600; }
.search-results .card .card-meta { margin: 2px 0 0; }

/* ---------- footer ---------- */
.foot {
  text-align: center; color: var(--muted);
  font-size: .82rem; padding: 20px;
  border-top: 1px solid var(--line);
  background: var(--card);
}

/* ---------- responsive ---------- */
@media (max-width: 860px) {
  .course-grid { grid-template-columns: 1fr; }
  .course-toc { position: static; }
  .page-head { grid-template-columns: 1fr; }
  .head-cover { max-width: none; }
}
@media (max-width: 640px) {
  .wrap { padding: 18px 14px 40px; }
  .hero { padding: 34px 22px 30px; border-radius: 14px; }
  .lesson-body { padding: 20px 18px; }
  .lesson-nav { grid-template-columns: 1fr; }
  .lesson-nav > span { display: none; }
  .lesson-top { flex-direction: column; align-items: flex-start; }
  .search input { width: 100%; }
  .nav { width: 100%; }
  .lesson-progress-strip { top: 57px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; }
}