:root {
  --bg: #ffffff;
  --fg: #14181f;
  --muted: #6b7280;
  --card: #f4f6f9;
  --border: #e2e6ec;
  --accent: #2f5597;
  --accent-fg: #ffffff;
  --ok: #1f9d55;
  --radius: 12px;
  --pad: 14px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #17191d;
    --fg: #e8eaed;
    --muted: #9aa0a6;
    --card: #21242a;
    --border: #2e3238;
    --accent: #4c7dd8;
    --ok: #27ae60;
  }
}

* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }

html, body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 15px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

#app { min-height: 100vh; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: calc(var(--pad) + env(safe-area-inset-top)) var(--pad) var(--pad);
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}

.topbar__back {
  flex: none;
  width: 34px;
  height: 34px;
  border: 1px solid var(--border);
  border-radius: 50%;
  background: var(--card);
  color: var(--fg);
  font-size: 22px;
  line-height: 1;
  padding: 0 0 3px;
  cursor: pointer;
}

.topbar__text { min-width: 0; flex: 1; }
.topbar__crumb { font-size: 11px; letter-spacing: .04em; text-transform: uppercase; color: var(--muted); }
.topbar__title {
  font-size: 16px;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.topbar__progress {
  flex: none;
  font-size: 12px;
  font-variant-numeric: tabular-nums;
  color: var(--muted);
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 4px 10px;
}

.progressbar { height: 3px; background: var(--border); }
.progressbar__fill { height: 100%; width: 0; background: var(--ok); transition: width .25s ease; }

/* ---------- generic view ---------- */
.view { padding: var(--pad) var(--pad) 28px; }
.view--lesson { padding-bottom: 96px; }

.hint { color: var(--muted); font-size: 13px; padding: 8px 2px 14px; }

/* ---------- экран выбора курса ---------- */
.course {
  display: block;
  width: 100%;
  text-align: left;
  padding: 14px 16px;
  margin-bottom: 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  color: inherit;
  font: inherit;
  cursor: pointer;
}
.course:active { transform: scale(.995); }
.course__head { display: flex; align-items: baseline; gap: 8px; }
.course__title { flex: 1; font-size: 16px; font-weight: 600; }
.course__count { flex: none; font-size: 12px; color: var(--muted); font-variant-numeric: tabular-nums; }
.course__subtitle { display: block; margin-top: 4px; font-size: 13px; color: var(--fg); opacity: .85; }
.course__meta { display: block; margin-top: 6px; font-size: 12.5px; color: var(--muted); }
.course__bar {
  display: block;
  height: 4px;
  margin-top: 10px;
  border-radius: 999px;
  background: var(--border);
  overflow: hidden;
}
.course__bar-fill { display: block; height: 100%; width: 0; background: var(--ok); transition: width .25s ease; }

.sync {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  margin: 0 2px 4px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  font-size: 12.5px;
  color: var(--muted);
  line-height: 1.45;
}
.sync__state { flex: 1; }
.sync__btn {
  flex: none;
  align-self: center;
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--fg);
  font: inherit;
  font-size: 12.5px;
  cursor: pointer;
  white-space: nowrap;
}
.sync__btn:disabled { opacity: .5; cursor: default; }

.footnote {
  margin: 18px 2px 0;
  padding-top: 12px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 12px;
  line-height: 1.5;
}
.footnote p { margin: 0; }
.footnote a { color: var(--accent); }

.row {
  display: flex;
  align-items: center;
  gap: 12px;
  width: 100%;
  text-align: left;
  padding: 12px 14px;
  margin-bottom: 8px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  color: inherit;
  font: inherit;
  cursor: pointer;
}

.row:active { transform: scale(.995); }
.row__index {
  flex: none;
  width: 26px;
  text-align: right;
  color: var(--muted);
  font-size: 13px;
  font-variant-numeric: tabular-nums;
}
.row__body { flex: 1; min-width: 0; }
.row__title { font-weight: 600; }
.row__sub {
  color: var(--muted);
  font-size: 12.5px;
  margin-top: 2px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.row__meta { flex: none; font-size: 12px; color: var(--muted); font-variant-numeric: tabular-nums; }
.row__count { flex: none; font-size: 12px; color: var(--muted); font-variant-numeric: tabular-nums; }
.row.is-done .row__title { color: var(--muted); }
.row.is-done .row__index { color: var(--ok); }

.dot { flex: none; width: 18px; text-align: center; color: var(--border); font-size: 15px; }
.dot.is-done { color: var(--ok); }

.search {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
}
.search__input {
  flex: 1;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  color: var(--fg);
  font: inherit;
}
.search__clear {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  color: var(--fg);
  padding: 0 12px;
  cursor: pointer;
}

.section-title {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: .05em;
  color: var(--muted);
  margin: 18px 2px 8px;
}

/* ---------- lesson body ---------- */
.lesson__head { margin-bottom: 14px; }
.lesson__title { font-size: 20px; line-height: 1.3; margin: 0 0 8px; }
.lesson__links { display: flex; gap: 12px; flex-wrap: wrap; }
.lesson__link { font-size: 13px; color: var(--accent); text-decoration: none; }

.lesson-body { overflow-wrap: break-word; }
.lesson-body > :first-child { margin-top: 0; }
.lesson-body h1, .lesson-body h2 { font-size: 19px; line-height: 1.3; margin: 26px 0 10px; }
.lesson-body h3 { font-size: 16px; margin: 20px 0 8px; }
.lesson-body h4 { font-size: 15px; margin: 16px 0 6px; }
.lesson-body p { margin: 10px 0; }
.lesson-body ul, .lesson-body ol { padding-left: 22px; }
.lesson-body li { margin: 4px 0; }
.lesson-body img, .lesson-body video { max-width: 100%; height: auto; border-radius: 8px; }
.lesson-body a { color: var(--accent); }
.lesson-body hr { border: 0; border-top: 1px solid var(--border); margin: 20px 0; }
.lesson-body blockquote {
  margin: 12px 0;
  padding: 8px 14px;
  border-left: 3px solid var(--accent);
  background: var(--card);
  border-radius: 0 8px 8px 0;
}
.lesson-body .text-bold, .lesson-body b, .lesson-body strong { font-weight: 600; }
.lesson-body .text-italic { font-style: italic; }

.lesson-body .code {
  display: inline-block;
  padding: 1px 6px;
  border-radius: 6px;
  background: var(--card);
  border: 1px solid var(--border);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: .88em;
  white-space: pre-wrap;
}
.lesson-body .code.text-user { color: #2f6fd8; border-color: #2f6fd855; }
.lesson-body .code.text-orange { color: #c2731a; border-color: #c2731a55; }
.lesson-body .code.text-green { color: #1f9d55; border-color: #1f9d5555; }
.lesson-body .code.text-red { color: #cf3c3c; border-color: #cf3c3c55; }
.lesson-body .code.text-viola { color: #8b5cf6; border-color: #8b5cf655; }

.lesson-body pre {
  margin: 12px 0;
  padding: 12px 14px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow-x: auto;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 13px;
  line-height: 1.5;
}
.lesson-body pre code { font: inherit; background: none; border: 0; padding: 0; }
.lesson-body pre .code, .lesson-body pre span.code { border: 0; padding: 0; background: none; }

.lesson-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 12px 0;
  font-size: 13.5px;
  display: block;
  overflow-x: auto;
}
.lesson-body th, .lesson-body td { border: 1px solid var(--border); padding: 6px 9px; text-align: left; vertical-align: top; }
.lesson-body th { background: var(--card); }

/* site promo/widget noise from the scraped pages */
.lesson-body .featured-content,
.lesson-body .task-widget-card,
.lesson-body .post-source-meta,
.lesson-body .stars,
.lesson-body .dark-matter { display: none !important; }

.lesson-body .table-container { overflow-x: auto; }
.lesson-body .icon-wrap, .lesson-body svg { display: none; }

/* ---------- bottom lesson nav ---------- */
.lesson-nav {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 20;
  display: grid;
  grid-template-columns: 1fr 1.15fr 1fr;
  gap: 8px;
  padding: 10px var(--pad) calc(10px + env(safe-area-inset-bottom));
  background: var(--bg);
  border-top: 1px solid var(--border);
}

.lesson-nav[hidden] { display: none; }

.nav-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-height: 46px;
  padding: 8px 6px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  color: var(--fg);
  font: inherit;
  font-size: 13px;
  cursor: pointer;
}
.nav-btn:disabled { opacity: .4; cursor: default; }
.nav-btn__arrow { font-size: 18px; line-height: 1; }
.nav-btn__label { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }

.nav-btn--done { background: var(--bg); }
.nav-btn--done.is-done {
  background: var(--ok);
  border-color: var(--ok);
  color: #fff;
  font-weight: 600;
}
.nav-btn--done .nav-btn__check { font-size: 16px; line-height: 1; color: var(--muted); }
.nav-btn--done.is-done .nav-btn__check { color: #fff; }

.loading { color: var(--muted); padding: 20px 2px; }
.error { color: #cf3c3c; padding: 20px 2px; }