/* Node.js Study Book — shared styles (light + dark) */
:root {
  --bg: #fbfaf7;
  --bg-soft: #f2f0ea;
  --panel: #ffffff;
  --text: #1f2328;
  --muted: #5d636b;
  --border: #e1ddd3;
  --accent: #2c7a33;          /* Node.js green, darkened for contrast */
  --accent-2: #2f5fa7;
  --accent-soft: #e4f2e2;
  --ana-bg: #f3ecfb; --ana-bd: #7b4bb7;
  --code-bg: #f5f3ee;
  --code-text: #1f2328;
  --code-head: #ebe7de;
  --c-comment: #6a737d;
  --c-string: #0a7d32;
  --c-keyword: #8f2fb3;
  --c-number: #b35900;
  --c-prompt: #2f5fa7;
  --tip-bg: #e9f6ec;  --tip-bd: #2e8b57;
  --note-bg: #e8f0fb; --note-bd: #2f5fa7;
  --pit-bg: #fff4dd;  --pit-bd: #c98a00;
  --bad-bg: #fdeaea;  --bad-bd: #c0392b;
  --good-bg: #e9f6ec; --good-bd: #2e8b57;
  --easy: #2e8b57; --medium: #b07d00; --hard: #c0392b;
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 4px 14px rgba(0,0,0,.04);
  --radius: 10px;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  /* no theme chosen yet (scripts off): follow the OS */
  :root:not([data-theme]) {
    --bg: #15171b;
    --bg-soft: #1c1f24;
    --panel: #1d2026;
    --text: #e6e6e3;
    --muted: #a3a8b0;
    --border: #30343c;
    --accent: #7fd17a;
    --accent-2: #7fb0ff;
    --accent-soft: #1b2e1c;
    --ana-bg: #251c33; --ana-bd: #c39bff;
    --code-bg: #101215;
    --code-text: #e3e3df;
    --code-head: #1a1d22;
    --c-comment: #8b949e;
    --c-string: #8fd694;
    --c-keyword: #d6a2ff;
    --c-number: #ffb86b;
    --c-prompt: #7fb0ff;
    --tip-bg: #15291d;  --tip-bd: #4fbf7f;
    --note-bg: #172235; --note-bd: #7fb0ff;
    --pit-bg: #2d2511;  --pit-bd: #e5b53b;
    --bad-bg: #331a1a;  --bad-bd: #ff7b72;
    --good-bg: #15291d; --good-bd: #4fbf7f;
    --easy: #4fbf7f; --medium: #e5b53b; --hard: #ff7b72;
    --shadow: 0 1px 3px rgba(0,0,0,.4);
    color-scheme: dark;
  }
}
/* the theme chosen in the site header (shared/site.js) */
:root[data-theme="dark"] {
  --bg: #15171b;
  --bg-soft: #1c1f24;
  --panel: #1d2026;
  --text: #e6e6e3;
  --muted: #a3a8b0;
  --border: #30343c;
  --accent: #7fd17a;
  --accent-2: #7fb0ff;
  --accent-soft: #1b2e1c;
  --ana-bg: #251c33; --ana-bd: #c39bff;
  --code-bg: #101215;
  --code-text: #e3e3df;
  --code-head: #1a1d22;
  --c-comment: #8b949e;
  --c-string: #8fd694;
  --c-keyword: #d6a2ff;
  --c-number: #ffb86b;
  --c-prompt: #7fb0ff;
  --tip-bg: #15291d;  --tip-bd: #4fbf7f;
  --note-bg: #172235; --note-bd: #7fb0ff;
  --pit-bg: #2d2511;  --pit-bd: #e5b53b;
  --bad-bg: #331a1a;  --bad-bd: #ff7b72;
  --good-bg: #15291d; --good-bd: #4fbf7f;
  --easy: #4fbf7f; --medium: #e5b53b; --hard: #ff7b72;
  --shadow: 0 1px 3px rgba(0,0,0,.4);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16.5px/1.65 var(--sans);
}
a { color: var(--accent); }
a:hover { text-decoration-thickness: 2px; }
code, kbd {
  font-family: var(--mono);
  font-size: .9em;
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 5px;
  padding: .05em .35em;
  overflow-wrap: anywhere;
}
kbd { border-bottom-width: 2px; }

/* ---------- layout ---------- */
.layout {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  min-height: 100vh;
}
#sidebar {
  position: sticky; top: 0; align-self: start;
  height: 100vh; overflow-y: auto;
  background: var(--bg-soft);
  border-right: 1px solid var(--border);
  padding: 18px 14px 40px;
  font-size: 14.5px;
}
#sidebar details > summary { display: none; }
#sidebar .all-courses {
  display: block; margin: 0 6px 12px; padding: 6px 10px; border-radius: 7px;
  border: 1px solid var(--border); background: var(--panel); color: var(--accent);
  font-weight: 600; font-size: 13.5px; text-decoration: none;
}
#sidebar .all-courses:hover { border-color: var(--accent); }
#sidebar .brand { display: block; font-weight: 700; font-size: 17px; color: var(--text); text-decoration: none; margin: 0 6px 14px; }
#sidebar .brand span { color: var(--accent); }
#sidebar .part { font-size: 11.5px; text-transform: uppercase; letter-spacing: .07em; color: var(--muted); margin: 16px 6px 4px; font-weight: 600; }
#sidebar ol { list-style: none; margin: 0; padding: 0; }
#sidebar li a {
  display: flex; gap: 8px; align-items: baseline;
  padding: 5px 8px; border-radius: 7px;
  color: var(--text); text-decoration: none;
}
#sidebar li a .num { color: var(--muted); font-variant-numeric: tabular-nums; min-width: 1.6em; font-size: 13px; }
#sidebar li a:hover { background: var(--accent-soft); }
#sidebar li a.current { background: var(--accent); color: var(--bg); font-weight: 600; }
#sidebar li a.current .num { color: var(--bg); }

main.content {
  max-width: 860px; width: 100%;
  margin: 0 auto;
  padding: 36px 32px 80px;
}
@media (max-width: 900px) {
  .layout { display: block; }
  #sidebar { position: static; height: auto; border-right: 0; border-bottom: 1px solid var(--border); padding: 10px 16px; }
  #sidebar details > summary { display: block; cursor: pointer; font-weight: 700; padding: 6px 0; }
  #sidebar .brand { display: none; }
  #sidebar .all-courses { display: inline-block; margin: 2px 0 6px; }
  main.content { padding: 22px 16px 60px; }
}

/* ---------- typography ---------- */
h1 { font-size: 2.1rem; line-height: 1.2; margin: .2em 0 .3em; letter-spacing: -.01em; }
h2 { font-size: 1.45rem; margin: 2.2em 0 .6em; padding-top: .4em; border-top: 1px solid var(--border); }
h3 { font-size: 1.15rem; margin: 1.6em 0 .5em; }
.eyebrow { text-transform: uppercase; letter-spacing: .08em; font-size: 12.5px; font-weight: 700; color: var(--accent); }
.lead { font-size: 1.15rem; color: var(--muted); margin-top: 0; }
hr { border: 0; border-top: 1px solid var(--border); margin: 2em 0; }

/* ---------- boxes ---------- */
.learn, .recap {
  background: var(--panel); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 14px 20px; box-shadow: var(--shadow);
  margin: 1.4em 0;
}
.learn h2, .recap h2 { border: 0; margin: .2em 0 .4em; padding: 0; font-size: 1.1rem; }
.learn { border-left: 5px solid var(--accent); }
.recap { border-left: 5px solid var(--accent-2); }

.tip, .note, .pitfall, .bad, .good, .older, .java, .browser, .analogy {
  border-left: 4px solid; border-radius: 8px;
  padding: 10px 16px; margin: 1.1em 0;
}
.tip { background: var(--tip-bg); border-color: var(--tip-bd); }
.note, .older, .java, .browser { background: var(--note-bg); border-color: var(--note-bd); }
.analogy { background: var(--ana-bg); border-color: var(--ana-bd); }
.pitfall { background: var(--pit-bg); border-color: var(--pit-bd); }
.bad { background: var(--bad-bg); border-color: var(--bad-bd); }
.good { background: var(--good-bg); border-color: var(--good-bd); }
.tip > :first-child, .note > :first-child, .pitfall > :first-child, .bad > :first-child,
.good > :first-child, .older > :first-child, .java > :first-child,
.browser > :first-child, .analogy > :first-child { margin-top: .2em; }
.tip > :last-child, .note > :last-child, .pitfall > :last-child, .bad > :last-child,
.good > :last-child, .older > :last-child, .java > :last-child,
.browser > :last-child, .analogy > :last-child { margin-bottom: .2em; }

.compare { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 1em 0; }
.compare > div { min-width: 0; }
.compare > .bad, .compare > .good { margin: 0; }
@media (max-width: 700px) { .compare { grid-template-columns: 1fr; } }

/* ---------- tables ---------- */
.table-wrap { overflow-x: auto; margin: 1em 0; }
table { border-collapse: collapse; width: 100%; font-size: .95em; background: var(--panel); }
th, td { border: 1px solid var(--border); padding: 7px 10px; text-align: left; vertical-align: top; }
th { background: var(--bg-soft); }

/* ---------- code blocks ---------- */
.codeblock {
  margin: 1em 0; border: 1px solid var(--border); border-radius: var(--radius);
  overflow: hidden; background: var(--code-bg);
}
.codeblock .code-head {
  display: flex; justify-content: space-between; align-items: center;
  background: var(--code-head); padding: 4px 8px 4px 12px;
  font: 12.5px var(--mono); color: var(--muted);
  border-bottom: 1px solid var(--border);
}
.codeblock .copy {
  font: 12px var(--sans); cursor: pointer;
  border: 1px solid var(--border); background: var(--panel); color: var(--text);
  border-radius: 6px; padding: 2px 10px;
}
.codeblock .copy:hover { border-color: var(--accent); }
.codeblock pre {
  margin: 0; padding: 12px 14px; overflow-x: auto;
  font: 14px/1.55 var(--mono); color: var(--code-text);
  tab-size: 4;
}
.codeblock pre code { background: none; border: 0; padding: 0; font-size: inherit; border-radius: 0; overflow-wrap: normal; }
.tok-c { color: var(--c-comment); font-style: italic; }
.tok-s { color: var(--c-string); }
.tok-k { color: var(--c-keyword); font-weight: 600; }
.tok-n { color: var(--c-number); }
.tok-p { color: var(--c-prompt); font-weight: 700; }
.tok-o { color: var(--muted); }
.tok-err { color: var(--hard); }

/* ---------- exercises ---------- */
.exercise {
  background: var(--panel); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 12px 18px; margin: 1.2em 0;
  box-shadow: var(--shadow);
}
.exercise h3 { margin: .3em 0 .4em; display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.lvl {
  display: inline-block; font-size: 12px; font-weight: 700;
  padding: 1px 9px; border-radius: 99px; border: 1px solid; white-space: nowrap;
}
.lvl.easy { color: var(--easy); border-color: var(--easy); }
.lvl.medium { color: var(--medium); border-color: var(--medium); }
.lvl.hard { color: var(--hard); border-color: var(--hard); }
.kind { font-size: 12px; color: var(--muted); font-weight: 500; }
details.solution { margin: .6em 0 .3em; border-top: 1px dashed var(--border); padding-top: .5em; }
details.solution > summary { cursor: pointer; color: var(--accent); font-weight: 600; }
details.solution[open] > summary { margin-bottom: .4em; }
details.check { background: var(--bg-soft); border-radius: 8px; padding: 8px 14px; margin: .8em 0; }
details.check > summary { cursor: pointer; font-weight: 600; }

/* ---------- index cards ---------- */
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 14px; margin: 1em 0 2em; }
.card {
  display: block; text-decoration: none; color: var(--text);
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 16px; box-shadow: var(--shadow); transition: border-color .15s, transform .15s;
}
.card:hover { border-color: var(--accent); transform: translateY(-1px); }
.card .num { font-size: 12px; font-weight: 700; color: var(--accent); text-transform: uppercase; letter-spacing: .06em; }
.card h3 { margin: .2em 0 .3em; font-size: 1.05rem; }
.card p { margin: 0; color: var(--muted); font-size: .92rem; }

/* ---------- buttons ---------- */
.btn {
  display: inline-block; cursor: pointer; text-decoration: none;
  font: 600 15px var(--sans); padding: 9px 18px; border-radius: 8px;
  border: 1px solid var(--border); background: var(--panel); color: var(--text);
}
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--bg); }
.btn.primary:hover { filter: brightness(1.08); }
.btn:disabled { opacity: .45; cursor: not-allowed; }

/* ---------- pager ---------- */
#pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 3em; padding-top: 1.2em; border-top: 1px solid var(--border); }
#pager a {
  flex: 1; text-decoration: none; border: 1px solid var(--border); border-radius: var(--radius);
  padding: 10px 14px; background: var(--panel); color: var(--text); min-width: 0;
}
#pager a:hover { border-color: var(--accent); }
#pager a small { display: block; color: var(--muted); font-size: 12px; }
#pager a.next { text-align: right; }
#pager .spacer { flex: 1; }

.doclinks li { margin: .2em 0; }

/* ---------- version badges ("Node 22+") ---------- */
.es {
  display: inline-block; font: 700 11px var(--mono); letter-spacing: .02em;
  padding: 1px 7px; border-radius: 99px; vertical-align: 2px;
  border: 1px solid var(--accent); color: var(--accent); background: var(--accent-soft);
  white-space: nowrap;
}
.es.es6 { border-color: var(--accent-2); color: var(--accent-2); }
h2 .es, h3 .es { margin-left: 6px; }
#sidebar .all-courses + .all-courses { margin-top: -6px; }

/* ---------- diagrams ---------- */
.diagram { margin: 1.2em 0; background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 12px; overflow-x: auto; }
.diagram svg { display: block; max-width: 100%; height: auto; margin: 0 auto; }
.diagram figcaption { color: var(--muted); font-size: .9rem; text-align: center; margin-top: 6px; }
.diagram .bx { fill: var(--bg-soft); stroke: var(--border); }
.diagram .hi { fill: var(--accent-soft); stroke: var(--accent); }
.diagram text { fill: var(--text); font: 13px var(--sans); }
.diagram .mut { fill: var(--muted); font-size: 12px; }
.diagram .ln { stroke: var(--muted); fill: none; stroke-width: 1.5; }
.diagram .ar { fill: var(--muted); }