/* ============================================================
   Atlas — Lesson page
   Reuses the tokens defined in styles.css (--nav-bg, --accent, ...).
   ============================================================ */

.lesson-shell {
  display: grid;
  grid-template-columns: 250px minmax(0, 1fr);
  gap: 48px;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 40px 24px 80px;
  align-items: start;
}

/* ---------- SIDEBAR ---------- */
.lesson-side { position: sticky; top: 92px; }

.side-kicker {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--text-light);
  margin-bottom: 10px;
}

.side-module { margin-bottom: 26px; }

.side-module-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--nav-bg);
  margin-bottom: 8px;
}

.side-list { border-left: 2px solid var(--border); }

.side-link {
  display: block;
  padding: 7px 12px;
  font-size: 0.86rem;
  line-height: 1.4;
  color: var(--text-light);
  border-left: 2px solid transparent;
  margin-left: -2px;
}

.side-link:hover { color: var(--nav-bg); background: var(--bg-alt); }

.side-link.is-current {
  color: var(--nav-bg);
  font-weight: 700;
  border-left-color: var(--accent);
  background: #FFF6F1;
}

.side-back {
  display: inline-block;
  font-size: 0.82rem;
  color: var(--text-light);
  margin-top: 4px;
}
.side-back:hover { color: var(--accent); }

/* ---------- ARTICLE ---------- */
.lesson-article { min-width: 0; max-width: 760px; }

.lesson-eyebrow {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

.lesson-h1 {
  font-size: 2.05rem;
  line-height: 1.22;
  letter-spacing: -0.015em;
  color: var(--nav-bg);
}

.lesson-dek {
  font-size: 1.12rem;
  color: var(--text-light);
  margin-top: 12px;
  line-height: 1.55;
}

.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  margin: 18px 0 26px;
}

.pill {
  font-size: 0.74rem;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--bg-alt);
  color: var(--text-light);
  border: 1px solid var(--border);
}

.pill-level { background: #EEF4FF; color: #1D4ED8; border-color: #D6E4FF; }

.lesson-objectives {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 22px;
  margin-bottom: 34px;
}

.lesson-objectives h2 {
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-light);
  margin-bottom: 10px;
}

.lesson-objectives ul { list-style: none; }

.lesson-objectives li {
  position: relative;
  padding-left: 22px;
  font-size: 0.94rem;
  margin-bottom: 6px;
}

.lesson-objectives li::before {
  content: "→";
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: 700;
}

/* ---------- BLOCKS ---------- */
.lesson-body h2 {
  font-size: 1.4rem;
  color: var(--nav-bg);
  margin: 42px 0 14px;
  letter-spacing: -0.01em;
  scroll-margin-top: 88px;
}

.lesson-body p {
  margin-bottom: 16px;
  font-size: 1.01rem;
  line-height: 1.72;
  color: #23304C;
}

.lesson-body p code,
.lesson-body li code {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 5px;
  font-size: 0.88em;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
}

.lesson-body a { color: var(--accent); text-decoration: underline; }

.lesson-body ul,
.lesson-body ol { margin: 0 0 18px 22px; }

.lesson-body li {
  margin-bottom: 9px;
  line-height: 1.65;
  font-size: 1rem;
  list-style: disc;
}

.lesson-body ol li { list-style: decimal; }

/* tables */
.lesson-table-wrap {
  overflow-x: auto;
  margin: 20px 0 26px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.lesson-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
  min-width: 520px;
}

.lesson-table caption {
  caption-side: top;
  text-align: left;
  padding: 10px 14px 0;
  font-size: 0.78rem;
  color: var(--text-light);
  font-weight: 600;
}

.lesson-table th {
  background: var(--nav-bg);
  color: #fff;
  text-align: left;
  padding: 10px 14px;
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  font-weight: 700;
}

.lesson-table td {
  padding: 11px 14px;
  border-top: 1px solid var(--border);
  vertical-align: top;
  line-height: 1.55;
}

.lesson-table tbody tr:nth-child(even) { background: #FAFBFE; }
.lesson-table td:first-child { font-weight: 600; color: var(--nav-bg); }

/* callouts */
.callout {
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 22px 0;
  border-left: 4px solid var(--accent);
  background: #FFF7F3;
  font-size: 0.97rem;
  line-height: 1.65;
}

.callout-title {
  font-weight: 700;
  color: var(--nav-bg);
  margin-bottom: 4px;
  font-size: 0.92rem;
}

.callout-note { background: #F4F7FF; border-left-color: #2C64D6; }
.callout-tip { background: #F1FAF4; border-left-color: #12855A; }
.callout-warn { background: #FFF8EC; border-left-color: #C27400; }
.callout-interview { background: #FAF5FF; border-left-color: #6D28D9; }

/* steps */
.steps { counter-reset: step; margin: 22px 0 26px; }

.step {
  position: relative;
  padding: 0 0 20px 46px;
  border-left: 2px solid var(--border);
  margin-left: 14px;
}

.step:last-child { border-left-color: transparent; padding-bottom: 0; }

.step::before {
  counter-increment: step;
  content: counter(step);
  position: absolute;
  left: -15px;
  top: 0;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-size: 0.8rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

.step-title {
  font-weight: 700;
  color: var(--nav-bg);
  margin-bottom: 4px;
  line-height: 1.5;
  font-size: 0.98rem;
}

.step-text { font-size: 0.97rem; line-height: 1.65; color: #3A4964; }

/* numbers grid */
.numbers-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 14px;
  margin: 22px 0 26px;
}

.number-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  background: #fff;
  box-shadow: var(--card-shadow);
}

.number-label {
  font-size: 0.76rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-light);
  font-weight: 700;
}

.number-value {
  font-size: 1.28rem;
  font-weight: 700;
  color: var(--accent);
  margin: 4px 0 6px;
}

.number-note { font-size: 0.85rem; color: var(--text-light); line-height: 1.5; }

/* mistakes */
.mistake {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  overflow: hidden;
  margin-bottom: 12px;
}

.mistake-side { padding: 13px 16px; font-size: 0.92rem; line-height: 1.55; }

.mistake-wrong { background: #FFF5F5; color: #8A2B2B; }
.mistake-right { background: #F2FBF6; color: #14603C; }

.mistake-tag {
  display: block;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 5px;
  opacity: 0.7;
}

/* qa */
.qa-item {
  border-bottom: 1px solid var(--border);
  padding: 16px 0;
}

.qa-q { font-weight: 700; color: var(--nav-bg); margin-bottom: 6px; font-size: 1rem; }
.qa-a { font-size: 0.97rem; line-height: 1.68; color: #3A4964; }

/* code */
.code-block {
  margin: 22px 0 26px;
  background: #0B1F4B;
  color: #E3EAF7;
  border-radius: var(--radius-sm);
  padding: 18px 20px;
  overflow-x: auto;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.84rem;
  line-height: 1.7;
  white-space: pre;
}

/* ---------- TAKEAWAYS + CHECKPOINT ---------- */
.lesson-takeaways {
  margin-top: 48px;
  border: 1px solid #D6E4FF;
  background: #F5F9FF;
  border-radius: var(--radius);
  padding: 22px 24px;
}

.lesson-takeaways h2 {
  font-size: 1.05rem;
  color: var(--nav-bg);
  margin-bottom: 12px;
}

.lesson-takeaways li {
  list-style: none;
  position: relative;
  padding-left: 24px;
  margin-bottom: 9px;
  font-size: 0.96rem;
  line-height: 1.6;
}

.lesson-takeaways li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: #12855A;
  font-weight: 700;
}

.checkpoint {
  margin-top: 40px;
  border-top: 2px solid var(--nav-bg);
  padding-top: 26px;
}

.checkpoint h2 {
  font-size: 1.3rem;
  color: var(--nav-bg);
  margin-bottom: 6px;
}

.checkpoint-note { font-size: 0.9rem; color: var(--text-light); margin-bottom: 20px; }

.q-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: 16px;
  background: #fff;
}

.q-text { font-weight: 700; color: var(--nav-bg); margin-bottom: 12px; }

.q-options { display: flex; flex-direction: column; gap: 8px; }

.q-option {
  text-align: left;
  font: inherit;
  font-size: 0.94rem;
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: #fff;
  cursor: pointer;
  color: var(--text);
  transition: border-color 0.15s, background 0.15s;
}

.q-option:hover:not(:disabled) { border-color: var(--accent); background: #FFF9F6; }
.q-option:disabled { cursor: default; }
.q-option.is-correct { border-color: #12855A; background: #F1FAF4; font-weight: 600; }
.q-option.is-wrong { border-color: #C0392B; background: #FFF5F5; }

.q-why {
  margin-top: 12px;
  font-size: 0.9rem;
  line-height: 1.6;
  color: #3A4964;
  background: var(--bg-alt);
  border-radius: var(--radius-sm);
  padding: 10px 14px;
  display: none;
}

.q-card.is-answered .q-why { display: block; }

.checkpoint-score {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--nav-bg);
  margin-top: 8px;
}

/* ---------- PREV / NEXT ---------- */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 46px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.lesson-nav a {
  flex: 1;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 18px;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.lesson-nav a:hover { border-color: var(--accent); box-shadow: var(--card-shadow); }

.lesson-nav .dir {
  display: block;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-light);
  font-weight: 700;
  margin-bottom: 3px;
}

.lesson-nav .name { font-size: 0.94rem; font-weight: 600; color: var(--nav-bg); }
.lesson-nav .next { text-align: right; }

/* ---------- LESSON LIST / 404 ---------- */
.lesson-shell-single { grid-template-columns: minmax(0, 1fr); }
.lesson-shell-single .lesson-article { max-width: 860px; }

.module-block { margin-top: 46px; }

.module-block-title {
  font-size: 1.35rem;
  color: var(--nav-bg);
  margin-bottom: 6px;
}

.module-block-desc {
  color: var(--text-light);
  font-size: 0.95rem;
  margin-bottom: 18px;
}

.lesson-rows { display: grid; gap: 10px; }

.lesson-row {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  padding: 16px 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: #fff;
  box-shadow: var(--card-shadow);
  transition: border-color 0.15s, box-shadow 0.15s;
}

.lesson-row:hover {
  border-color: var(--accent);
  box-shadow: var(--card-shadow-hover);
}

.lr-num {
  flex: 0 0 auto;
  background: var(--accent);
  color: #fff;
  font-size: 0.72rem;
  font-weight: 700;
  border-radius: 4px;
  padding: 3px 8px;
  margin-top: 2px;
}

.lr-main { flex: 1 1 auto; min-width: 0; }

.lr-title {
  display: block;
  font-weight: 700;
  color: var(--nav-bg);
  font-size: 1rem;
  margin-bottom: 3px;
}

.lr-dek {
  display: block;
  font-size: 0.88rem;
  color: var(--text-light);
  line-height: 1.5;
}

.lr-meta {
  flex: 0 0 auto;
  font-size: 0.78rem;
  color: var(--text-light);
  white-space: nowrap;
  margin-top: 3px;
}

/* ---------- RESPONSIVE ---------- */
@media (max-width: 900px) {
  .lesson-shell { grid-template-columns: 1fr; gap: 26px; padding: 26px 18px 60px; }
  .lesson-side { position: static; }
  .lesson-h1 { font-size: 1.65rem; }
  .mistake { grid-template-columns: 1fr; }
  .lesson-nav { flex-direction: column; }
  .lesson-nav .next { text-align: left; }
  .lesson-row { flex-wrap: wrap; }
  .lr-meta { width: 100%; margin-left: 46px; }
}