/* Shared lesson rhythm. Keep short answers, reasoning, and code distinct. */
body:not(.catalog-page) .dsa-main {
  max-width: 1280px;
  padding: 28px 32px 48px;
}
body:not(.catalog-page) .lesson-head {
  margin: 24px 0 16px;
  align-items: start;
}
body:not(.catalog-page) .lesson-head h1 {
  font-size: clamp(28px, 3.2vw, 42px);
  line-height: 1.2;
  margin: 8px 0 12px;
}
body:not(.catalog-page) .lesson-head p {
  max-width: 76ch;
  font-size: 15px;
  line-height: 1.7;
}
body:not(.catalog-page) .lesson-meta {
  display: none;
}
.dsa-main #content {
  min-width: 0;
}
.dsa-main #content > * + * {
  margin-top: 20px;
}
.dsa-main #content > .action-row {
  padding-top: 20px;
  border-top: 1px solid var(--line);
  margin-top: 28px;
}
.dsa-main .panel-pad {
  padding: 24px;
}
.dsa-main .panel-label {
  padding: 12px 24px;
  font-size: 11px;
  letter-spacing: 0.08em;
}
.dsa-main .prose {
  font-size: 15px;
  line-height: 1.8;
}
.dsa-main .prose > p {
  max-width: 85ch;
}
.dsa-main h2 {
  font-size: 23px;
  line-height: 1.35;
}
.dsa-main .prose h2 {
  margin-bottom: 14px;
}
.dsa-main .prose h3 {
  margin: 22px 0 10px;
  font-size: 18px;
}
.dsa-main .prose > :first-child {
  margin-top: 0;
}
.dsa-main .prose p + p {
  margin-top: 14px;
}
.dsa-main .prose dl {
  display: grid;
  grid-template-columns: 110px minmax(0, 1fr);
  gap: 12px 20px;
  margin: 24px 0;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--code);
}
.dsa-main .prose dt {
  text-transform: capitalize;
  color: var(--ink);
  font-size: 13px;
}
.dsa-main .prose dd {
  margin: 0;
  font-size: 14px;
  overflow-wrap: anywhere;
}
.dsa-main button {
  min-height: 44px;
}
.dsa-main :is(input, textarea, select):focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
}
.dsa-main .stages {
  gap: 8px;
  margin: 0 0 24px;
  padding-top: 4px;
}
.dsa-main .stages button {
  justify-content: center;
  font-size: 13px;
  padding: 12px 8px;
  min-height: 48px;
  line-height: 1.45;
}
.dsa-main .case-tabs {
  gap: 8px;
  margin: 0 0 20px;
}
.dsa-main .case-tabs button {
  background: var(--surface);
  font-size: 12px;
  padding: 10px 13px;
  text-align: left;
}
.dsa-main .case-tabs button[aria-pressed="true"] {
  background: color-mix(in srgb, var(--gold) 9%, var(--surface));
}
.dsa-main .draft-label {
  font-size: 14px;
  font-weight: 600;
  margin: 22px 0 10px;
  line-height: 1.5;
}
.dsa-main textarea {
  border: 1px solid var(--line);
  border-radius: 9px;
  padding: 14px 16px;
  resize: vertical;
  font-size: 14px;
  line-height: 1.7;
}
.dsa-main textarea.approach {
  height: 128px;
  min-height: 100px;
  margin: 0 0 16px;
  font-family: var(--sans);
}
.dsa-main #prediction {
  height: 96px;
  min-height: 80px;
  font-family: var(--mono);
  margin-bottom: 14px;
}
.dsa-main #implementation {
  height: 360px;
  min-height: 220px;
  font-family: var(--mono);
}
.dsa-main #custom-tests {
  height: 200px;
  min-height: 120px;
  margin: 12px 0 16px;
}
.dsa-main .small-note {
  font-size: 13px;
  line-height: 1.65;
}
.practice-heading {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 22px;
}
.practice-heading > span {
  white-space: nowrap;
  font: 12px var(--mono);
  color: var(--muted);
}
.prediction-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr);
  gap: 28px;
  align-items: start;
}
.prediction-layout > section {
  min-width: 0;
}
.practice-input {
  padding: 18px;
  background: var(--code);
  border: 1px solid var(--line);
  border-radius: 10px;
}
.practice-response {
  padding: 2px 0;
}
.practice-response .draft-label {
  margin-top: 0;
}
.practice-response #prediction-format {
  margin: 0 0 12px;
}
.practice-response .reveal {
  margin: 18px 0 12px;
}
.dsa-main #prediction-feedback:not(:empty),
.dsa-main #run-results:not(:empty),
.dsa-main #custom-results:not(:empty) {
  padding: 14px 16px;
  margin: 16px 0;
  border: 1px solid var(--line);
  background: var(--code);
  border-radius: 9px;
  font-size: 14px;
  line-height: 1.75;
  overflow-wrap: anywhere;
}
#prediction-feedback[data-state="correct"] {
  border-left: 3px solid var(--cyan) !important;
}
#prediction-feedback[data-state="retry"] {
  border-left: 3px solid var(--gold) !important;
}
.dsa-main #manual-answer:not(:empty) {
  margin-top: 24px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}
.dsa-main .reveal {
  margin: 20px 0;
}
.dsa-main .reveal summary {
  padding: 12px 16px;
  min-height: 44px;
  font-size: 14px;
}
.dsa-main .reveal > p {
  margin: 12px 0;
  font-size: 14px;
  line-height: 1.75;
}
.dsa-main .input-data {
  margin: 16px 0 0;
}
.dsa-main .input-data summary {
  padding: 8px 0;
  min-height: 36px;
  font-size: 13px;
}
.dsa-main .input-data pre {
  padding: 12px;
  margin: 8px 0 0;
  max-height: 260px;
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--code);
}
.dsa-main .pointer-strip {
  gap: 8px;
  margin: 12px 0;
}
.dsa-main .pointer-strip span {
  padding: 6px 10px;
  font-size: 13px;
  border-color: var(--line);
  background: var(--surface);
}
.dsa-main .structure-view {
  padding: 8px;
}
.dsa-main .worked-example > h3 {
  font-size: 19px;
  margin: 0 0 20px;
}
.dsa-main .example-label {
  line-height: 1.5;
}
.dsa-main .answer-summary {
  margin-top: 16px;
  padding: 14px 16px;
}
.dsa-main .answer-summary p {
  font-size: 14px;
}
.dsa-main .trace-grid {
  padding: 20px 0 0;
  gap: 24px;
}
.dsa-main .trace-shell .trace-grid {
  padding: 20px;
}
.dsa-main .code-lines li {
  font-size: 13px;
  line-height: 1.8;
}
.dsa-main #source,
.dsa-main #trace-code {
  max-height: 560px;
}
.dsa-main #trace-status {
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 9px;
  background: var(--code);
  margin-top: 14px;
  font-size: 14px;
  line-height: 1.7;
}
.dsa-main #trace-scrub {
  display: block;
  margin: 10px 0;
  min-height: 28px;
  accent-color: var(--gold);
}
.dsa-main .panel-pad:has(> #trace-example) > .action-row {
  justify-content: flex-start;
  margin: 12px 0 18px;
  gap: 8px;
}
.dsa-main .panel-pad:has(> #implementation) > .action-row {
  justify-content: flex-start;
  margin-top: 14px;
  gap: 10px;
}
.dsa-main .panel-pad > label:not(.draft-label) {
  display: block;
  margin: 12px 0 6px;
  font-size: 13px;
  color: var(--muted);
}
.dsa-main th,
.dsa-main td {
  font-size: 12px;
  padding: 9px 12px;
}
.dsa-main .visual-grid td {
  font-size: 13px;
}
.dsa-main .table-scroll {
  max-width: 100%;
}
.dsa-main .footer-note {
  font-size: 12px;
  line-height: 1.75;
}
@media (max-width: 900px) {
  .prediction-layout {
    grid-template-columns: 1fr;
    gap: 22px;
  }
  .practice-input .structure-view {
    max-height: 340px;
  }
  .practice-response {
    max-width: 100%;
  }
  .dsa-main .stages {
    gap: 2px;
  }
  .dsa-main .stages button {
    font-size: 12px;
    padding: 10px 5px;
  }
}
@media (max-width: 600px) {
  body:not(.catalog-page) .dsa-main {
    padding: 20px 12px 36px;
  }
  body:not(.catalog-page) .topbar {
    position: relative;
  }
  .dsa-main .panel-pad {
    padding: 18px 16px;
  }
  .dsa-main .panel-label {
    padding: 12px 16px;
  }
  .dsa-main h2 {
    font-size: 21px;
  }
  .dsa-main .prose dl {
    grid-template-columns: 1fr;
    gap: 5px;
    padding: 16px;
  }
  .dsa-main .prose dd + dt {
    margin-top: 12px;
  }
  .dsa-main .stages {
    display: flex;
    overflow-x: auto;
    padding-bottom: 4px;
  }
  .dsa-main .stages button {
    flex: 0 0 auto;
    flex-direction: row;
    padding: 12px;
    font-size: 12px;
  }
  .practice-heading {
    display: block;
  }
  .practice-heading > span {
    display: block;
    margin-top: 8px;
  }
  .practice-input {
    padding: 12px;
  }
  .dsa-main .case-tabs {
    flex-wrap: nowrap;
    overflow-x: auto;
    padding-bottom: 6px;
  }
  .dsa-main .case-tabs button {
    flex-shrink: 0;
    max-width: 220px;
  }
  .dsa-main .trace-grid {
    gap: 20px;
  }
  .dsa-main .trace-shell .trace-grid {
    padding: 16px;
  }
  .dsa-main textarea,
  .dsa-main input {
    font-size: 16px;
  }
  .dsa-main .code-lines li {
    font-size: 12px;
  }
  .dsa-main .structure-view {
    max-height: 340px;
  }
  .dsa-main .learning-choices button {
    text-align: left;
  }
}
.dsa-main .lesson-trace-controls {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 12px 24px;
  flex-wrap: wrap;
}
.dsa-main .lesson-trace-controls > div {
  min-width: 0;
  max-width: 100%;
}
.dsa-main .lesson-trace-controls label {
  display: block;
  font-size: 13px;
  color: var(--muted);
  margin-bottom: 6px;
}
.dsa-main .lesson-trace-controls select {
  margin: 0;
  min-height: 44px;
  width: 100%;
}
.dsa-main .lesson-trace-controls .action-row {
  justify-content: flex-start;
  margin: 0;
  gap: 8px;
}
.dsa-main .lesson-timeline {
  display: flex;
  gap: 16px;
  align-items: center;
  margin-top: 14px;
}
.dsa-main .lesson-timeline label {
  color: var(--muted);
  font-size: 12px;
}
.dsa-main .lesson-timeline #trace-scrub {
  flex: 1;
  min-width: 0;
  margin: 0;
}
.dsa-main .panel-pad > .prose:not(.worked-example) {
  max-width: 90ch;
}
.dsa-main .approach-explanation + h3 {
  margin-top: 22px;
}
/* Stage navigation stays reachable independently of lesson length. */
html { scroll-padding-bottom: calc(100px + env(safe-area-inset-bottom, 0px)); }
body:not(.catalog-page) .dsa-main { padding-bottom: calc(112px + env(safe-area-inset-bottom, 0px)); }
.dsa-main #content > .lesson-navigation {
  position: fixed;
  inset: auto 0 0;
  z-index: 30;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: nowrap;
  gap: 12px;
  margin: 0;
  padding: 12px max(16px, calc((100vw - 1216px) / 2));
  padding-bottom: calc(12px + env(safe-area-inset-bottom, 0px));
  border-top: 1px solid var(--line);
  background: var(--surface);
  box-shadow: 0 -8px 24px #00000014;
}
.lesson-navigation > :last-child { margin-left: auto; }
.lesson-navigation > a { display: inline-flex; align-items: center; min-height: 44px; font-size: 13px; }
.lesson-navigation .small-note { margin: 0; }
body:not(.catalog-page) .completion-toast { bottom: calc(88px + env(safe-area-inset-bottom, 0px)); }
@media(max-width:600px) {
  .lesson-navigation .small-note { display: none; }
  .dsa-main #content > .lesson-navigation { gap: 8px; padding-left: 12px; padding-right: 12px; }
  .lesson-navigation > button,.lesson-navigation > a { font-size: 12px; padding: 10px 12px; }
}
.trace-state { margin-top:20px; }
.dsa-main .trace-key { font:12px/1.65 var(--sans); color:var(--muted); margin:8px 0 12px; }
.trace-values { display:grid; grid-template-columns:repeat(auto-fit,minmax(120px,1fr)); gap:8px; margin:12px 0; }
.trace-value { border:1px solid var(--line); border-radius:8px; padding:10px 12px; min-width:0; }
.trace-value dt { font-size:12px; color:var(--muted); }
.dsa-main .trace-value dd { margin:4px 0 0; font:14px/1.6 var(--mono); overflow-wrap:anywhere; }
.trace-collection { border:1px solid var(--line); border-radius:10px; padding:14px; margin:14px 0; min-width:0; }
.trace-collection>header,.frame-view li>header { display:flex; flex-wrap:wrap; gap:6px 16px; justify-content:space-between; align-items:baseline; }
.trace-collection h4 { margin:0; font:600 14px var(--mono); }
.trace-collection header span,.frame-view small { color:var(--muted); font-size:11px; }
.trace-items { display:flex; gap:6px; flex-wrap:wrap; list-style:none; padding:0; margin:12px 0 0; }
.trace-items li { border:1px solid var(--line); border-radius:6px; padding:7px 10px; min-width:44px; max-width:100%; overflow-wrap:anywhere; }
.trace-items small { display:block; color:var(--muted); font:10px var(--mono); }
.trace-items code { font-size:13px; white-space:pre-wrap; }
.trace-items.stack { flex-direction:column; border-bottom:3px solid var(--line); max-width:320px; padding-bottom:6px; }
.trace-items.stack li:first-child { border-color:var(--gold); }
.trace-items.set li { border-radius:22px; }
.trace-map { margin:12px 0 0; }
.trace-map>div { display:grid; grid-template-columns:minmax(65px,.4fr) minmax(0,1fr); border-bottom:1px solid var(--line); gap:12px; padding:8px; }
.trace-map dt,.dsa-main .trace-map dd { font:12px/1.7 var(--mono); margin:0; overflow-wrap:anywhere; }
.trace-map dt { color:var(--cyan); }
.trace-empty,.trace-change { font-size:12px; color:var(--muted); padding:10px 0; }
.trace-matrix td small { display:block; color:var(--muted); font-size:10px; }
.frame-view { margin-top:24px; }
.frame-view h3 span { font-size:12px; font-weight:400; color:var(--muted); }
.frame-view ol { list-style:none; padding:0 0 8px; border-bottom:3px solid var(--line); display:grid; gap:8px; }
.frame-view li { border:1px solid var(--line); border-radius:8px; padding:12px; overflow-wrap:anywhere; }
.frame-view li.current-frame { border-left:3px solid var(--gold); }
.frame-view li p { font-size:12px; margin:8px 0 0; }
.frame-view li code { white-space:pre-wrap; }
.frame-return { color:var(--cyan); }
.helper-buttons { display:flex; gap:8px; flex-wrap:wrap; margin:12px 0; }
.helper-source { position:relative; max-height:300px; margin-top:16px; }
.dsa-main .panel:has(#source) { overflow:visible; }
.dsa-main .trace-grid:has(#source) > div:last-child { position:sticky; top:90px; align-self:start; }
.dsa-main #source { max-height:calc(100vh - 190px); }
@media(max-width:1000px) { .dsa-main .trace-grid:has(#source)>div:last-child { position:static; } .dsa-main #source { max-height:400px; } }