:root {
  --lesson-accent: #4a90e2;
  --lesson-accent-dark: #2b6fae;
  --lesson-accent-soft: #edf5fc;
  --lesson-navy: #102a43;
  --lesson-text: #182534;
  --lesson-muted: #5d6c7c;
  --lesson-border: #bad5ec;
  --lesson-bg: #f7fafc;
  --lesson-white: #fff;
  --lesson-font: Calibri, Carlito, Arial, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100vh;
  color: var(--lesson-text);
  background: var(--lesson-bg);
  font-family: var(--lesson-font);
  font-size: 16px;
  line-height: 1.48;
  text-align: right;
}

p, li, h1, h2, h3, a { text-align: right; }

.lesson-app {
  width: min(calc(100% - .8rem), 1420px);
  min-height: calc(100vh - .8rem);
  margin: .4rem auto;
  display: grid;
  grid-template-rows: auto 1fr auto;
  overflow: hidden;
  border: 1px solid var(--lesson-accent);
  border-radius: .9rem;
  background: var(--lesson-white);
}

.lesson-header {
  min-height: 58px;
  padding: .35rem .85rem;
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: .65rem;
  align-items: center;
  border-bottom: 1px solid var(--lesson-border);
}

.lesson-brand {
  display: flex;
  gap: .45rem;
  align-items: center;
  color: inherit;
  text-decoration: none;
}

.lesson-brand img { width: 50px; height: 31px; object-fit: contain; }
.lesson-brand span { display: grid; }
.lesson-brand strong { color: var(--lesson-navy); font-size: .92rem; }
.lesson-brand small { color: var(--lesson-muted); font-size: .68rem; }
.lesson-course { margin: 0; color: var(--lesson-muted); text-align: center; font-size: .88rem; }
.lesson-home { color: var(--lesson-navy); font-size: 1.1rem; text-decoration: none; }

.lesson-stage { padding: clamp(.7rem, 1.7vw, 1.2rem); }
.lesson-slide { display: none; min-height: 420px; }
.lesson-slide.is-active { display: block; }

.slide-code {
  display: inline-flex;
  padding: .12rem .45rem;
  border: 1px solid var(--lesson-accent);
  border-radius: 999px;
  color: var(--lesson-accent-dark);
  font-size: .64rem;
  font-weight: 800;
}

.title-slide {
  max-width: 980px;
  min-height: 420px;
  margin-inline: auto;
  display: grid;
  grid-template-columns: minmax(0, 1.55fr) minmax(130px, .45fr);
  gap: 1rem;
  align-items: center;
}

.title-slide__content h1 {
  margin: .42rem 0;
  color: var(--lesson-navy);
  font-size: clamp(1.85rem, 3.7vw, 3.1rem);
  line-height: 1.08;
}

.title-slide__content > p { max-width: 700px; margin: 0; color: var(--lesson-muted); }
.title-visual { min-height: 130px; display: grid; place-items: center; border-radius: 50%; background: var(--lesson-accent-soft); }
.title-visual img { width: min(95px, 62%); }

.lesson-purpose,
.info-box,
.rule-box,
.exercise-box,
.compact-card {
  border: 1px solid var(--lesson-border);
  border-radius: .62rem;
  background: var(--lesson-accent-soft);
}

.lesson-purpose { margin-top: .65rem; padding: .58rem .75rem; }
.lesson-purpose h2 { margin: 0 0 .1rem; color: var(--lesson-navy); font-size: .96rem; }
.lesson-purpose p { margin: .08rem 0; }

.text-slide,
.video-slide { max-width: 1000px; margin-inline: auto; }
.text-slide > h1,
.video-slide > h1 { margin: .42rem 0 .62rem; color: var(--lesson-navy); font-size: clamp(1.5rem, 2.8vw, 2.15rem); }
.text-slide h2 { margin: .58rem 0 .15rem; color: var(--lesson-accent-dark); font-size: 1.04rem; }
.text-slide p,
.text-slide li { margin-block: .32rem; font-size: 1rem; }

.compact-grid { display: grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap: .65rem; }
.compact-card { padding: .62rem .72rem; background: #fff; }
.compact-card h2 { margin-top: 0; }

.info-box,
.rule-box,
.exercise-box { margin-top: .55rem; padding: .62rem .75rem; }
.rule-box { border-inline-start: 4px solid var(--lesson-accent); }
.exercise-box { display: grid; grid-template-columns: 1fr auto; gap: .65rem; align-items: center; }
.exercise-link { display: inline-flex; justify-content: center; padding: .48rem .72rem; border-radius: .45rem; background: #dce5ec; color: #5c6d7b; font-weight: 800; }

.video-frame { width: min(100%, 790px); margin-inline: auto; aspect-ratio: 16 / 9; overflow: hidden; border: 1px solid var(--lesson-border); border-radius: .65rem; background: #0c1721; }
.video-frame iframe { width: 100%; height: 100%; border: 0; }
.video-note { width: min(100%, 790px); margin: .45rem auto 0; color: var(--lesson-muted); font-size: .9rem; }

.lesson-footer {
  min-height: 52px;
  padding: .32rem .7rem;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: .55rem;
  align-items: center;
  border-top: 1px solid var(--lesson-border);
}

.lesson-footer button { min-width: 90px; padding: .43rem .68rem; border: 1px solid var(--lesson-accent); border-radius: .45rem; background: #fff; color: var(--lesson-accent-dark); font: inherit; font-weight: 800; cursor: pointer; }
.lesson-footer button[data-next] { justify-self: end; background: var(--lesson-accent-dark); color: #fff; }
.lesson-footer button:disabled { opacity: .35; cursor: not-allowed; }
.lesson-pagination { margin: 0; color: var(--lesson-muted); font-weight: 700; }

@media (max-width: 820px) {
  .title-slide { min-height: auto; grid-template-columns: 1fr; }
  .title-visual { min-height: 90px; border-radius: .65rem; }
  .lesson-slide { min-height: auto; }
  .compact-grid { grid-template-columns: 1fr; }
}

@media (max-width: 620px) {
  .lesson-header { grid-template-columns: 1fr auto; }
  .lesson-course { grid-column: 1 / -1; grid-row: 2; text-align: right; }
  .lesson-brand small { display: none; }
  .exercise-box { grid-template-columns: 1fr; }
}