/* Shared lesson stylesheet — Tufte-inspired, print-friendly */
:root {
  --bg: #faf8f5;
  --fg: #1a1a1a;
  --muted: #5c5c5c;
  --accent: #0b5f8a;
  --accent-soft: #e6f2f8;
  --border: #d4cfc6;
  --card: #ffffff;
  --warn: #8a4b0b;
  --ok: #1e5c3a;
  --week1: #0b5f8a;
  --week2: #6b3fa0;
  --week3: #b45309;
  --maxw: 42rem;
  --font: "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua", Georgia, serif;
  --mono: "JetBrains Mono", "SF Mono", ui-monospace, Menlo, Consolas, monospace;
  --sans: "Source Sans 3", "Segoe UI", system-ui, sans-serif;
}

* { box-sizing: border-box; }
html { font-size: 18px; scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

.wrap {
  max-width: calc(var(--maxw) + 8rem);
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

header.lesson-header {
  border-bottom: 1px solid var(--border);
  padding-bottom: 1.25rem;
  margin-bottom: 1.75rem;
}
header.lesson-header .eyebrow {
  font-family: var(--sans);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.4rem;
}
header.lesson-header h1 {
  font-size: 1.85rem;
  font-weight: 600;
  line-height: 1.2;
  margin: 0 0 0.6rem;
  letter-spacing: -0.01em;
}
header.lesson-header .lede {
  color: var(--muted);
  font-size: 1.05rem;
  margin: 0;
  max-width: 38rem;
}

.meta-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  margin-top: 1rem;
  font-family: var(--sans);
  font-size: 0.8rem;
  color: var(--muted);
}
.meta-bar a { color: var(--accent); }

h2 {
  font-size: 1.25rem;
  margin: 2.2rem 0 0.75rem;
  font-weight: 600;
}
h3 {
  font-size: 1.05rem;
  margin: 1.4rem 0 0.5rem;
  font-weight: 600;
}
p { margin: 0.65rem 0; max-width: var(--maxw); }
ul, ol { max-width: var(--maxw); padding-left: 1.25rem; }
li { margin: 0.35rem 0; }
a { color: var(--accent); text-underline-offset: 2px; }
code, .id {
  font-family: var(--mono);
  font-size: 0.86em;
  background: var(--accent-soft);
  padding: 0.08em 0.35em;
  border-radius: 3px;
}

.note {
  max-width: var(--maxw);
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  padding: 0.75rem 1rem;
  margin: 1.25rem 0;
  font-family: var(--sans);
  font-size: 0.92rem;
}
.note strong { color: var(--accent); }

.ask-agent {
  max-width: var(--maxw);
  border: 1px dashed var(--border);
  background: var(--card);
  padding: 0.9rem 1rem;
  margin: 2rem 0 1rem;
  font-family: var(--sans);
  font-size: 0.92rem;
}
.ask-agent::before {
  content: "Ask your teacher";
  display: block;
  font-size: 0.72rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.35rem;
}

/* Flow diagram */
.flow {
  display: grid;
  gap: 0.75rem;
  margin: 1.25rem 0 1.75rem;
  max-width: 48rem;
}
.flow-week {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.1rem;
  box-shadow: 0 1px 0 rgba(0,0,0,0.03);
}
.flow-week h3 {
  margin: 0 0 0.35rem;
  font-family: var(--sans);
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.badge {
  font-family: var(--sans);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: #fff;
  padding: 0.15rem 0.45rem;
  border-radius: 999px;
}
.badge.w1 { background: var(--week1); }
.badge.w2 { background: var(--week2); }
.badge.w3 { background: var(--week3); }
.flow-week .q {
  font-style: italic;
  color: var(--muted);
  margin: 0 0 0.6rem;
  font-size: 0.95rem;
}
.flow-week .papers {
  font-family: var(--sans);
  font-size: 0.85rem;
  margin: 0;
  padding-left: 1.1rem;
  color: var(--fg);
}
.flow-week .papers li { margin: 0.2rem 0; }
.arrow-down {
  text-align: center;
  color: var(--muted);
  font-size: 1.25rem;
  line-height: 1;
  margin: -0.15rem 0;
}

/* Cards / axes */
.axes {
  display: grid;
  gap: 0.65rem;
  max-width: 48rem;
  margin: 1rem 0 1.5rem;
}
@media (min-width: 720px) {
  .axes { grid-template-columns: 1fr 1fr; }
}
.axis {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.85rem 1rem;
}
.axis h4 {
  margin: 0 0 0.35rem;
  font-family: var(--sans);
  font-size: 0.9rem;
}
.axis p {
  margin: 0;
  font-size: 0.9rem;
  color: var(--muted);
  max-width: none;
}

/* Quiz */
.quiz {
  max-width: 40rem;
  margin: 1.25rem 0 2rem;
  font-family: var(--sans);
}
.quiz-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.1rem;
  margin-bottom: 0.85rem;
}
.quiz-item p.qtext {
  margin: 0 0 0.75rem;
  font-family: var(--font);
  font-size: 1rem;
  max-width: none;
}
.quiz-item label {
  display: block;
  padding: 0.45rem 0.65rem;
  margin: 0.25rem 0;
  border-radius: 6px;
  border: 1px solid transparent;
  cursor: pointer;
  font-size: 0.9rem;
}
.quiz-item label:hover { background: var(--accent-soft); }
.quiz-item input { margin-right: 0.45rem; }
.quiz-item .feedback {
  display: none;
  margin-top: 0.65rem;
  font-size: 0.88rem;
  padding: 0.5rem 0.65rem;
  border-radius: 6px;
}
.quiz-item.answered .feedback { display: block; }
.feedback.ok { background: #e8f5ee; color: var(--ok); }
.feedback.bad { background: #f8eee6; color: var(--warn); }

.primary-source {
  max-width: var(--maxw);
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.1rem;
  margin: 1.25rem 0;
}
.primary-source h3 { margin-top: 0; }
.primary-source p { max-width: none; margin: 0.4rem 0; }

footer.lesson-footer {
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  font-family: var(--sans);
  font-size: 0.85rem;
  color: var(--muted);
  max-width: var(--maxw);
}
footer.lesson-footer a { color: var(--accent); }

@media print {
  body { background: #fff; font-size: 11pt; }
  .quiz, .ask-agent { break-inside: avoid; }
  a { color: inherit; text-decoration: none; }
}

/* Coupling looseness spectrum */
.spectrum {
  max-width: 50rem;
  margin: 1.25rem 0;
  font-family: var(--sans);
  font-size: 0.82rem;
}
.spectrum-labels {
  display: flex;
  justify-content: space-between;
  color: var(--muted);
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 0.35rem;
}
.spectrum-bar {
  display: flex;
  height: 0.5rem;
  border-radius: 999px;
  overflow: hidden;
  margin: 0 0 0.6rem;
  background: linear-gradient(to right, #e6f2f8, #c9e6d8, #f0e0b8, #f3c9b4, #e89a9a);
}
.spectrum-row {
  display: grid;
  grid-template-columns: 9rem 1fr;
  gap: 0.6rem;
  align-items: baseline;
  padding: 0.3rem 0;
  border-bottom: 1px dashed var(--border);
}
.spectrum-row:last-child { border-bottom: none; }
.spectrum-row .who { font-weight: 600; }
.spectrum-row .where { color: var(--muted); font-size: 0.8rem; }

/* Five-dimension design-space table */
.dim-table {
  width: 100%;
  max-width: 50rem;
  border-collapse: collapse;
  font-family: var(--sans);
  font-size: 0.84rem;
  margin: 1rem 0 1.5rem;
  background: var(--card);
}
.dim-table th, .dim-table td {
  border: 1px solid var(--border);
  padding: 0.5rem 0.6rem;
  vertical-align: top;
  text-align: left;
}
.dim-table th { background: var(--accent-soft); font-weight: 600; }
.dim-table td:first-child { font-weight: 600; white-space: nowrap; }

/* Formula / pipeline cards for model lessons */
.formula {
  max-width: min(100%, 48rem);
  background: var(--card);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: 6px;
  padding: 0.85rem 1rem;
  margin: 1rem 0;
  font-family: var(--mono);
  font-size: 0.84rem;
  line-height: 1.55;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  white-space: pre-wrap;
  word-break: break-word;
  overflow-wrap: anywhere;
}
.formula pre,
pre.formula {
  margin: 0;
  padding: 0;
  font: inherit;
  white-space: pre-wrap;
  word-break: break-word;
  overflow-wrap: anywhere;
  background: transparent;
  border: 0;
}
.formula .line {
  display: block;
  white-space: pre-wrap;
  word-break: break-word;
  margin: 0.15rem 0;
}
.formula .caption {
  display: block;
  font-family: var(--sans);
  font-size: 0.78rem;
  color: var(--muted);
  margin-top: 0.55rem;
  white-space: normal;
  word-break: normal;
  line-height: 1.45;
}
@media (max-width: 640px) {
  html { font-size: 16px; }
  .formula { font-size: 0.78rem; padding: 0.75rem 0.8rem; }
  .wrap { padding: 1.25rem 0.9rem 3rem; }
  .kv-table { font-size: 0.78rem; display: block; overflow-x: auto; -webkit-overflow-scrolling: touch; }
  .kv-table th { white-space: normal; }
  header.lesson-header h1 { font-size: 1.45rem; }
}
.pipeline {
  display: grid;
  gap: 0.55rem;
  max-width: 48rem;
  margin: 1rem 0 1.5rem;
}
.pipeline-step {
  display: grid;
  grid-template-columns: 2.2rem 1fr;
  gap: 0.75rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.75rem 0.9rem;
  align-items: start;
}
.pipeline-step .n {
  font-family: var(--sans);
  font-weight: 700;
  color: #fff;
  background: var(--accent);
  width: 1.8rem;
  height: 1.8rem;
  border-radius: 999px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
}
.pipeline-step h4 {
  margin: 0 0 0.2rem;
  font-family: var(--sans);
  font-size: 0.95rem;
}
.pipeline-step p {
  margin: 0;
  font-size: 0.9rem;
  color: var(--muted);
  max-width: none;
}
.kv-table {
  width: 100%;
  max-width: 48rem;
  border-collapse: collapse;
  font-family: var(--sans);
  font-size: 0.86rem;
  margin: 1rem 0 1.5rem;
  background: var(--card);
}
.kv-table th, .kv-table td {
  border: 1px solid var(--border);
  padding: 0.5rem 0.65rem;
  text-align: left;
  vertical-align: top;
}
.kv-table th { background: var(--accent-soft); font-weight: 600; white-space: nowrap; }
.decay-viz {
  max-width: 42rem;
  margin: 1rem 0 1.5rem;
  font-family: var(--sans);
  font-size: 0.82rem;
}
.decay-bars {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: 0.25rem;
  align-items: end;
  height: 7rem;
  margin: 0.5rem 0;
}
.decay-bars .bar {
  background: linear-gradient(to top, var(--accent), #6eb4d6);
  border-radius: 3px 3px 0 0;
  min-height: 2px;
  position: relative;
}
.decay-bars .bar span {
  position: absolute;
  bottom: -1.15rem;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0.65rem;
  color: var(--muted);
}
.talk-card {
  max-width: var(--maxw);
  background: #fffdf8;
  border: 1px solid #e8d9b8;
  border-radius: 8px;
  padding: 1rem 1.1rem;
  margin: 1rem 0;
  font-family: var(--sans);
  font-size: 0.92rem;
}
.talk-card h4 {
  margin: 0 0 0.45rem;
  font-size: 0.95rem;
  color: var(--warn);
}
.checklist {
  max-width: var(--maxw);
  list-style: none;
  padding: 0;
  margin: 1rem 0;
  font-family: var(--sans);
  font-size: 0.92rem;
}
.checklist li {
  padding: 0.45rem 0.65rem 0.45rem 2rem;
  margin: 0.3rem 0;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 6px;
  position: relative;
}
.checklist li::before {
  content: "☐";
  position: absolute;
  left: 0.65rem;
  color: var(--accent);
  font-weight: 700;
}
.warn-box {
  max-width: var(--maxw);
  border-left: 3px solid var(--warn);
  background: #fbf3e8;
  padding: 0.75rem 1rem;
  margin: 1.25rem 0;
  font-family: var(--sans);
  font-size: 0.92rem;
}
.ok-box {
  max-width: var(--maxw);
  border-left: 3px solid var(--ok);
  background: #eef7f1;
  padding: 0.75rem 1rem;
  margin: 1.25rem 0;
  font-family: var(--sans);
  font-size: 0.92rem;
}