* { box-sizing: border-box; }
:root {
  --bg: #0c0a09;
  --bg-soft: #1c1917;
  --bg-soft-2: #292524;
  --border: #44403c;
  --border-soft: #292524;
  --text: #f5f5f4;
  --text-soft: #a8a29e;
  --text-dim: #78716c;
  --accent: #eab308;
  --accent-soft: #fbbf24;
  --read: #22c55e;
  --link: #fde68a;
  --code-bg: #0c0a09;
}

html, body { height: 100%; margin: 0; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: Georgia, 'Iowan Old Style', 'Times New Roman', serif;
  -webkit-font-smoothing: antialiased;
}

.layout { display: grid; grid-template-columns: 320px 1fr; min-height: 100vh; }

/* ------------ sidebar ------------ */
.sidebar {
  background: var(--bg-soft);
  border-right: 1px solid var(--border);
  padding: 16px 0;
  display: flex; flex-direction: column;
  position: sticky; top: 0; height: 100vh; overflow: hidden;
}
.brand { padding: 0 16px 12px; border-bottom: 1px solid var(--border-soft); }
.brand .back { color: var(--text-dim); font-size: 12px; text-decoration: none; }
.brand .back:hover { color: var(--accent); }
.brand h1 { color: var(--accent); font-size: 22px; margin: 6px 0 4px; letter-spacing: .3px; }
.brand .meta { color: var(--text-dim); font-size: 12px; margin: 0; font-family: ui-monospace, monospace; }

.search { padding: 12px 16px; border-bottom: 1px solid var(--border-soft); }
.search input {
  width: 100%; padding: 8px 10px;
  background: var(--bg); color: var(--text);
  border: 1px solid var(--border); border-radius: 6px;
  font: inherit; font-size: 13px; font-family: system-ui, sans-serif;
}
.search input:focus { outline: none; border-color: var(--accent); }

.tree { flex: 1; overflow-y: auto; padding: 8px 0; }
.tree::-webkit-scrollbar { width: 8px; }
.tree::-webkit-scrollbar-track { background: transparent; }
.tree::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

.section { margin: 0 0 4px; }
.section-head {
  display: flex; align-items: center; gap: 6px;
  width: 100%;
  padding: 8px 16px;
  background: transparent; border: 0;
  color: var(--text-soft);
  font: 600 12px/1.3 system-ui, sans-serif;
  text-transform: uppercase; letter-spacing: .5px;
  cursor: pointer; text-align: left;
}
.section-head:hover { color: var(--text); background: var(--bg-soft-2); }
.section-head .num { color: var(--text-dim); font-variant-numeric: tabular-nums; min-width: 22px; }
.section-head .caret { margin-left: auto; transition: transform .15s; color: var(--text-dim); }
.section.collapsed .caret { transform: rotate(-90deg); }
.section.collapsed .files { display: none; }
.section-progress { font-size: 10px; color: var(--text-dim); margin-left: 6px; }

.files { list-style: none; margin: 0; padding: 0; }
.file-link {
  display: flex; align-items: center; gap: 8px;
  width: 100%;
  padding: 7px 16px 7px 28px;
  background: transparent; border: 0;
  color: var(--text-soft);
  font: 13px/1.4 system-ui, sans-serif;
  cursor: pointer; text-align: left;
  border-left: 2px solid transparent;
}
.file-link:hover { background: var(--bg-soft-2); color: var(--text); }
.file-link.active {
  color: var(--accent);
  border-left-color: var(--accent);
  background: rgba(234,179,8,.07);
}
.file-link.read::before {
  content: ''; width: 6px; height: 6px; border-radius: 50%;
  background: var(--read); flex-shrink: 0;
}
.file-link:not(.read)::before {
  content: ''; width: 6px; height: 6px; border-radius: 50%;
  background: transparent; border: 1px solid var(--border); flex-shrink: 0;
}

.legend {
  padding: 10px 16px; border-top: 1px solid var(--border-soft);
  display: flex; align-items: center; gap: 8px;
  color: var(--text-dim); font: 11px/1 system-ui, sans-serif;
}
.legend .dot { width: 8px; height: 8px; border-radius: 50%; }
.legend .dot.read { background: var(--read); }
.legend .reset {
  margin-left: auto;
  background: transparent; border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 3px 8px; border-radius: 4px;
  cursor: pointer; font: inherit;
}
.legend .reset:hover { border-color: var(--accent); color: var(--accent); }

/* ------------ content ------------ */
.content { padding: 32px 48px 96px; max-width: 100%; min-width: 0; }
.menu-btn { display: none; }

.article { max-width: 760px; margin: 0 auto; }

.welcome { color: var(--text-soft); padding: 40px 0; }
.welcome h2 { color: var(--accent); font-size: 32px; margin: 0 0 12px; }
.welcome .lead { font-size: 17px; line-height: 1.6; margin-bottom: 24px; }
.welcome .stats {
  list-style: none; margin: 24px 0; padding: 0;
  display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
  font-family: system-ui, sans-serif;
}
.welcome .stats li {
  background: var(--bg-soft); border: 1px solid var(--border);
  padding: 14px 16px; border-radius: 8px;
}
.welcome .stats b { color: var(--accent); font-size: 22px; display: block; }
.welcome .stats span { color: var(--text-dim); font-size: 12px; }
.welcome .hint { color: var(--text-dim); font-size: 13px; margin-top: 32px; font-family: system-ui, sans-serif; }
.welcome kbd {
  background: var(--bg-soft-2); border: 1px solid var(--border); border-radius: 4px;
  padding: 1px 6px; font: 12px ui-monospace, monospace; color: var(--link);
}

/* markdown styles — учебник */
.article h1 { color: var(--accent); font-size: 30px; margin: 0 0 8px; line-height: 1.25; }
.article h2 { color: var(--accent-soft); font-size: 22px; margin: 32px 0 12px; line-height: 1.3; border-bottom: 1px solid var(--border-soft); padding-bottom: 6px; }
.article h3 { color: var(--text); font-size: 18px; margin: 24px 0 10px; }
.article h4 { color: var(--text); font-size: 16px; margin: 20px 0 8px; }
.article p { line-height: 1.7; margin: 0 0 14px; }
.article ul, .article ol { line-height: 1.65; padding-left: 22px; margin: 0 0 14px; }
.article li { margin: 4px 0; }
.article strong { color: var(--accent-soft); }
.article em { color: var(--text); font-style: italic; }
.article code {
  background: var(--bg-soft-2); border: 1px solid var(--border-soft);
  padding: 1px 6px; border-radius: 4px;
  font: 14px ui-monospace, monospace; color: var(--link);
}
.article pre {
  background: var(--code-bg); border: 1px solid var(--border);
  padding: 12px 14px; border-radius: 8px;
  overflow-x: auto;
  font: 13px/1.5 ui-monospace, monospace; color: var(--text);
}
.article pre code { background: transparent; border: 0; padding: 0; color: inherit; }
.article blockquote {
  margin: 14px 0; padding: 10px 16px;
  border-left: 3px solid var(--accent);
  background: rgba(234,179,8,.06);
  color: var(--text-soft); font-style: italic;
}
.article blockquote p:last-child { margin-bottom: 0; }
.article hr { border: 0; border-top: 1px solid var(--border-soft); margin: 28px 0; }
.article a { color: var(--link); text-decoration: underline; text-decoration-color: var(--border); }
.article a:hover { text-decoration-color: var(--accent); }

.article table {
  width: 100%; border-collapse: collapse; margin: 14px 0;
  font: 14px/1.5 system-ui, sans-serif;
}
.article th, .article td {
  border: 1px solid var(--border); padding: 8px 12px; text-align: left; vertical-align: top;
}
.article th { background: var(--bg-soft); color: var(--accent-soft); font-weight: 600; }
.article tr:nth-child(even) td { background: rgba(255,255,255,.02); }

.crumbs { color: var(--text-dim); font: 12px/1 system-ui, sans-serif; margin-bottom: 16px; }
.crumbs span { color: var(--text-soft); }

/* footer nav */
.filebar {
  position: fixed; bottom: 0; left: 320px; right: 0;
  background: rgba(12,10,9,.92); backdrop-filter: blur(8px);
  border-top: 1px solid var(--border);
  padding: 10px 48px;
  display: flex; align-items: center; gap: 12px;
  z-index: 5;
}
.filebar .navbtn, .filebar .mark {
  background: var(--bg-soft); border: 1px solid var(--border);
  color: var(--text); padding: 7px 14px; border-radius: 6px;
  font: 13px system-ui, sans-serif; cursor: pointer;
}
.filebar .navbtn:hover, .filebar .mark:hover { border-color: var(--accent); color: var(--accent); }
.filebar .navbtn:disabled { opacity: .4; cursor: not-allowed; }
.filebar .mark.is-read { border-color: var(--read); color: var(--read); }
.filebar .filenav { margin-left: auto; display: flex; gap: 8px; }

/* ------------ mobile ------------ */
@media (max-width: 800px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed; left: 0; top: 0; height: 100vh; width: 86%; max-width: 340px;
    z-index: 50; transform: translateX(-100%); transition: transform .2s;
    box-shadow: 4px 0 20px rgba(0,0,0,.5);
  }
  .layout.menu-open .sidebar { transform: translateX(0); }
  .layout.menu-open::after {
    content: ''; position: fixed; inset: 0; background: rgba(0,0,0,.5); z-index: 40;
  }
  .content { padding: 16px 18px 96px; }
  .menu-btn {
    display: inline-block;
    background: var(--bg-soft); border: 1px solid var(--border);
    color: var(--text); padding: 6px 12px; border-radius: 6px;
    font: 14px system-ui, sans-serif; cursor: pointer;
    margin-bottom: 16px;
  }
  .filebar { left: 0; padding: 8px 16px; }
  .article h1 { font-size: 24px; }
  .article h2 { font-size: 19px; }
  .welcome h2 { font-size: 24px; }
}