/* Intro to Blockchain and Cryptocurrency — student site
   Offline, printable, no webfonts, no frameworks. */

:root {
  --ink: #1c1916;
  --muted: #5c564e;
  --paper: #f6f1e8;
  --card: #fffdf8;
  --line: #d9d0c2;
  --accent: #8b1e1e;
  --accent-soft: #f3e4df;
  --ok: #2d4a3e;
  --max: 44rem;
  --nav-h: 3.25rem;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font: 17px/1.55 "Source Serif 4", "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
}

.skip {
  position: absolute;
  left: -999px;
}
.skip:focus {
  left: 1rem;
  top: 1rem;
  z-index: 20;
  background: var(--card);
  padding: 0.4rem 0.7rem;
}

/* --- top bar --- */

.top {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--ink);
  color: #f6f1e8;
  min-height: var(--nav-h);
}

.top-inner {
  max-width: 72rem;
  margin: 0 auto;
  padding: 0.55rem 1.25rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.65rem 1.25rem;
}

.brand {
  color: #f6f1e8;
  text-decoration: none;
  font: 600 0.82rem/1.2 system-ui, "Segoe UI", sans-serif;
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

.brand span {
  display: block;
  font-weight: 400;
  opacity: 0.7;
  text-transform: none;
  letter-spacing: 0;
  font-size: 0.75rem;
  margin-top: 0.1rem;
}

nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.2rem 0.35rem;
  font: 500 0.86rem/1 system-ui, "Segoe UI", sans-serif;
}

nav a {
  color: #f6f1e8;
  text-decoration: none;
  padding: 0.4rem 0.55rem;
  border-radius: 3px;
}

nav a:hover { background: #3a342e; }

nav a[aria-current="page"] {
  background: var(--accent);
}

/* --- page frame --- */

.page {
  max-width: 72rem;
  margin: 0 auto;
  padding: 1.75rem 1.25rem 4rem;
}

.layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

.layout.has-toc {
  grid-template-columns: 15.5rem 1fr;
  align-items: start;
}

@media (max-width: 880px) {
  .layout.has-toc { grid-template-columns: 1fr; }
  .toc { position: static !important; }
}

.article { max-width: var(--max); }

.kicker {
  font: 600 0.78rem/1.3 system-ui, "Segoe UI", sans-serif;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 0.4rem;
}

h1 {
  font-size: 2rem;
  line-height: 1.2;
  font-weight: 650;
  margin: 0 0 0.85rem;
  letter-spacing: -0.02em;
}

h2 {
  font-size: 1.28rem;
  margin: 2.1rem 0 0.7rem;
  padding-top: 0.4rem;
  border-top: 1px solid var(--line);
}

h3 {
  font-size: 1.05rem;
  margin: 1.4rem 0 0.45rem;
}

h4 { font-size: 1rem; margin: 1.1rem 0 0.35rem; }

p, li { margin: 0 0 0.75rem; }

li p { margin-bottom: 0.35rem; }

ul, ol { padding-left: 1.25rem; }

blockquote {
  margin: 1rem 0;
  padding: 0.15rem 0 0.15rem 1rem;
  border-left: 3px solid var(--accent);
  color: var(--muted);
}

hr {
  border: 0;
  border-top: 1px solid var(--line);
  margin: 1.75rem 0;
}

a { color: var(--accent); }

code, .math {
  font-family: "Cascadia Mono", "Consolas", "Menlo", monospace;
  font-size: 0.86em;
  background: var(--accent-soft);
  padding: 0.08em 0.28em;
}

pre {
  background: #231f1b;
  color: #f6f1e8;
  padding: 0.9rem 1rem;
  overflow: auto;
  font-size: 0.86rem;
  line-height: 1.45;
}

pre code {
  background: none;
  color: inherit;
}

pre.mermaid {
  background: #f6f1e8;
  color: #231f1b;
  border: 1px solid var(--line);
  text-align: center;
  overflow-x: auto;
}
  padding: 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
  margin: 0.9rem 0 1.2rem;
  background: var(--card);
}

th, td {
  border: 1px solid var(--line);
  padding: 0.45rem 0.6rem;
  text-align: left;
  vertical-align: top;
}

th {
  background: #efe7d8;
  font: 600 0.78rem/1.35 system-ui, "Segoe UI", sans-serif;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

tr:nth-child(even) td { background: #faf6ee; }

.rule {
  background: var(--accent-soft);
  border: 1px solid #e2c4bc;
  padding: 0.75rem 1rem;
  margin: 1.1rem 0;
}

.rule strong:first-child { color: var(--accent); }

/* --- TOC --- */

.toc {
  position: sticky;
  top: calc(var(--nav-h) + 0.85rem);
  font: 500 0.8rem/1.35 system-ui, "Segoe UI", sans-serif;
  max-height: calc(100vh - var(--nav-h) - 1.5rem);
  overflow: auto;
  padding-right: 0.4rem;
}

.toc h2 {
  font: 600 0.72rem/1.2 system-ui, "Segoe UI", sans-serif;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  border: 0;
  margin: 0 0 0.6rem;
  padding: 0;
}

.toc ol {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc li { margin: 0 0 0.35rem; }

.toc a {
  color: var(--muted);
  text-decoration: none;
}

.toc a:hover { color: var(--accent); }

.toc .sub { padding-left: 0.7rem; font-weight: 400; }

/* --- cards on listing pages --- */

.cards {
  display: grid;
  gap: 0.75rem;
  margin: 1.25rem 0 2rem;
}

.card {
  display: block;
  background: var(--card);
  border: 1px solid var(--line);
  padding: 0.85rem 1rem;
  text-decoration: none;
  color: inherit;
}

.card:hover { border-color: var(--accent); }

.card b {
  display: block;
  font: 650 1rem/1.3 "Source Serif 4", Georgia, serif;
  color: var(--accent);
  margin-bottom: 0.2rem;
}

.card span {
  color: var(--muted);
  font-size: 0.92rem;
}

.meta {
  font: 500 0.88rem/1.45 system-ui, "Segoe UI", sans-serif;
  color: var(--muted);
  margin: 0 0 1.25rem;
}

.meta-grid {
  display: grid;
  grid-template-columns: 9rem 1fr;
  gap: 0.35rem 1rem;
  background: var(--card);
  border: 1px solid var(--line);
  padding: 0.85rem 1rem;
  margin: 0.9rem 0 1.2rem;
  font: 500 0.92rem/1.4 system-ui, "Segoe UI", sans-serif;
}

.meta-grid div { display: contents; }

.meta-grid strong { color: var(--muted); font-weight: 600; }

footer.site {
  max-width: 72rem;
  margin: 0 auto;
  padding: 0 1.25rem 2.5rem;
  color: var(--muted);
  font: 400 0.8rem/1.4 system-ui, "Segoe UI", sans-serif;
}

/* quizzes: room to write when printed */
.quiz-paper .article p { margin-bottom: 0.65rem; }
.quiz-paper ul { margin-bottom: 1rem; }

@media print {
  .top, .toc, footer.site, .skip { display: none !important; }
  body { background: white; font-size: 11.5pt; }
  .page { padding: 0; max-width: none; }
  .layout.has-toc { grid-template-columns: 1fr; }
  .article { max-width: none; }
  a { color: inherit; text-decoration: none; }
  table { break-inside: avoid; }
  h2, h3 { break-after: avoid; }
}