:root {
  --ink: #1a1a2e;
  --paper: #fafaf7;
  --accent: #2d5f8a;
  --rule: rgba(26, 26, 46, 0.18);
  --rule-strong: rgba(26, 26, 46, 0.38);
  --muted: rgba(26, 26, 46, 0.68);
  --ghost: rgba(26, 26, 46, 0.42);
  --surface: rgba(255, 255, 255, 0.52);
  --surface-strong: rgba(255, 255, 255, 0.74);
  --serif: "Source Serif 4", Georgia, serif;
  --sans: "Source Sans 3", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --mono: "JetBrains Mono", ui-monospace, Menlo, Consolas, monospace;
}

*,
*::before,
*::after { box-sizing: border-box; }

html { font-size: 16px; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  line-height: 1.58;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: inherit; }

.site {
  min-height: 100vh;
  display: grid;
  grid-template-rows: auto auto 1fr;
}

.masthead {
  border-top: 4px solid var(--ink);
  border-bottom: 1px solid var(--rule);
  padding: 1rem 1.5rem 0.95rem;
  display: flex;
  gap: 1rem;
  align-items: baseline;
  flex-wrap: wrap;
}

.brand {
  font-size: 1.28rem;
  font-weight: 700;
}

.brand small {
  margin-left: 0.8rem;
  font-family: var(--sans);
  font-size: 0.72rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.22em;
  color: var(--muted);
}

.header-meta {
  margin-left: auto;
  display: flex;
  gap: 0.85rem;
  flex-wrap: wrap;
  align-items: center;
}

.status-chip {
  padding: 0.18rem 0.52rem;
  border: 1px solid var(--rule-strong);
  font-family: var(--sans);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--muted);
}

.status-chip.live {
  color: var(--paper);
  background: var(--accent);
  border-color: var(--accent);
}

.student-slot {
  padding: 0.35rem 0.6rem 0.32rem;
  border: 1px solid var(--rule-strong);
  background: var(--surface);
  min-width: 11rem;
}

.student-slot .label {
  display: block;
  margin: 0 0 0.08rem;
  font-family: var(--sans);
  font-size: 0.62rem;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--ghost);
}

.student-slot .name {
  display: block;
  font-family: var(--serif);
  font-size: 1rem;
  color: var(--ink);
}

.nav {
  border-bottom: 1px solid var(--rule);
  padding: 0.65rem 1.5rem;
  display: flex;
  gap: 1.3rem;
  flex-wrap: wrap;
  align-items: center;
  font-family: var(--sans);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
}

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

.nav a.active {
  color: var(--ink);
  border-bottom: 1px solid var(--ink);
  padding-bottom: 0.15rem;
}

.nav .uri {
  margin-left: auto;
  font-family: var(--mono);
  font-size: 0.74rem;
  text-transform: none;
  letter-spacing: 0;
  color: var(--muted);
}

.shell {
  display: grid;
  grid-template-columns: 15.5rem minmax(0, 1fr) 17rem;
  min-height: 0;
}

.rail,
.context {
  background: var(--surface);
}

.rail {
  border-right: 1px solid var(--rule);
  padding: 1.1rem 0.95rem 1.8rem;
}

.context {
  border-left: 1px solid var(--rule);
  padding: 1.1rem 0.95rem 1.8rem;
}

.rail h2,
.context h2,
.side-section h3 {
  margin: 0 0 0.7rem;
  font-family: var(--serif);
  font-size: 1.05rem;
  font-weight: 500;
}

.side-section { margin-top: 1.4rem; }

.workspace {
  padding: 1.25rem;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  grid-template-rows: minmax(0, 1fr);
  min-height: 0;
  position: relative;
}

.pane {
  background: var(--surface-strong);
  border: 1px solid var(--rule);
  display: grid;
  min-height: 0;
}

.lesson-pane {
  grid-template-rows: auto 1fr;
  min-height: calc(100vh - 13.6rem);
}

.pane-head {
  border-bottom: 1px solid var(--rule);
  padding: 0.85rem 1rem;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: baseline;
  font-family: var(--sans);
  color: var(--muted);
}

.pane-head h2 {
  margin: 0;
  font-size: 1rem;
  color: var(--ink);
}

.pane-head-main {
  display: flex;
  gap: 0.75rem;
  align-items: baseline;
}

.lesson-scroll {
  overflow: auto;
  padding: 1.4rem;
}

.lesson-inner {
  max-width: 50rem;
}

.rail-list,
.status-list,
.resource-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.rail-list {
  display: grid;
  gap: 0.45rem;
}

.rail-list li {
  min-width: 0;
  padding: 0.5rem;
  border-left: 2px solid transparent;
}

.rail-list a,
.rail-list li[aria-disabled="true"] {
  min-width: 0;
  display: grid;
  grid-template-columns: 2.4rem minmax(0, 1fr);
  gap: 0.55rem;
  align-items: start;
  color: var(--ink);
  text-decoration: none;
}

.rail-list li.current {
  border-left-color: var(--accent);
  background: rgba(45, 95, 138, 0.08);
}

.rail-list .code,
.rail-list .state,
.status-list span,
.resource-list span:first-child {
  font-family: var(--sans);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--muted);
}

.rail-list .state {
  grid-column: 2;
  display: block;
  margin-top: 0.08rem;
}

.status-list,
.resource-list {
  display: grid;
  gap: 0.65rem;
}

.status-list li,
.resource-list li {
  display: grid;
  gap: 0.12rem;
  overflow-wrap: anywhere;
}

.status-list strong {
  font-weight: 600;
}

.rlp {
  max-width: 44rem;
}

.rlp-tab {
  display: inline-flex;
  text-decoration: none;
}

.rlp-checkpoint {
  margin-top: 1.2rem;
  padding: 1rem 0 0;
  border-top: 1px solid var(--rlp-line, var(--rule));
}

.rlp-checkpoint h2 {
  margin: 0 0 0.45rem;
  font-family: var(--rlp-serif, var(--serif));
  font-size: 1.18rem;
}

.code-slab,
.inline-command {
  overflow: auto;
  border: 1px solid var(--rule);
  background: #fff;
  color: var(--ink);
  font-family: var(--mono);
  font-size: 0.88rem;
  line-height: 1.55;
}

.code-slab {
  padding: 1rem;
}

.inline-command {
  margin: 0;
  padding: 0.75rem;
}

code {
  font-family: var(--mono);
  font-size: 0.92em;
}

.tutor-question-set {
  display: grid;
  gap: 0.8rem;
}

.tutor-card {
  border: 1px solid var(--rule);
  background: #fff;
}

.tutor-card summary {
  cursor: pointer;
  padding: 0.85rem 1rem;
  font-family: var(--sans);
  font-weight: 600;
}

.tutor-answer {
  border-top: 1px solid var(--rule);
  padding: 0.85rem 1rem 1rem;
}

.tutor-answer p {
  margin: 0.35rem 0;
}

.answer-label {
  display: inline-block;
  min-width: 4.4rem;
  margin-right: 0.4rem;
  font-family: var(--sans);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--muted);
}

.assessment-form {
  display: grid;
  gap: 1rem;
}

.assessment-item {
  border: 1px solid var(--rule);
  margin: 0;
  padding: 0.95rem 1rem 1rem;
  background: #fff;
}

.assessment-item legend {
  padding: 0 0.25rem;
  font-family: var(--sans);
  font-weight: 700;
}

.assessment-item label {
  display: grid;
  grid-template-columns: 1.1rem minmax(0, 1fr);
  gap: 0.55rem;
  align-items: start;
  margin-top: 0.65rem;
  cursor: pointer;
}

.assessment-item[data-state="correct"] {
  border-color: rgba(45, 95, 138, 0.58);
}

.assessment-item[data-state="incorrect"],
.assessment-item[data-state="missing"] {
  border-color: rgba(150, 55, 45, 0.52);
}

.assessment-actions {
  display: flex;
  gap: 0.7rem;
  flex-wrap: wrap;
}

.assessment-actions button {
  min-height: 2.35rem;
  border: 1px solid var(--ink);
  background: var(--ink);
  color: var(--paper);
  padding: 0.45rem 0.85rem;
  font-family: var(--sans);
  font-weight: 700;
  cursor: pointer;
}

.assessment-actions button[type="button"] {
  background: transparent;
  color: var(--ink);
}

.assessment-result {
  margin-top: 1.1rem;
  border: 1px solid var(--rule);
  padding: 1rem;
  background: var(--surface-strong);
}

.assessment-result p {
  margin: 0.2rem 0;
}

.result-kicker {
  font-family: var(--sans);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--muted);
}

.result-score {
  font-family: var(--serif);
  font-size: 2rem;
  line-height: 1.1;
}

.assessment-result[data-state="passed"] {
  border-color: rgba(45, 95, 138, 0.58);
}

.assessment-result[data-state="needs-review"],
.assessment-result[data-state="incomplete"] {
  border-color: rgba(150, 55, 45, 0.35);
}

.live-tutor-panel {
  margin: 1.15rem 0 1.35rem;
  border: 1px solid var(--rule);
  background: rgba(255, 255, 255, 0.58);
  padding: 1rem;
  display: grid;
  gap: 1rem;
}

.live-tutor-form {
  display: grid;
  gap: 0.7rem;
}

.live-tutor-label {
  font-family: var(--sans);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--muted);
}

.live-tutor-form textarea {
  width: 100%;
  min-height: 7.5rem;
  resize: vertical;
  border: 1px solid var(--rule-strong);
  background: var(--paper);
  color: var(--ink);
  padding: 0.85rem;
  font: 1rem/1.45 var(--serif);
}

.live-tutor-form textarea:focus {
  outline: 2px solid rgba(45, 95, 138, 0.32);
  outline-offset: 2px;
}

.live-tutor-actions {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.8rem;
  flex-wrap: wrap;
}

.live-tutor-boundary {
  font-family: var(--sans);
  font-size: 0.78rem;
  color: var(--muted);
}

.live-tutor-button {
  border: 1px solid var(--accent);
  background: var(--accent);
  color: var(--paper);
  padding: 0.5rem 0.9rem;
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.13em;
  cursor: pointer;
}

.live-tutor-button:disabled {
  cursor: wait;
  opacity: 0.62;
}

.live-tutor-output {
  border-top: 1px solid var(--rule);
  padding-top: 0.9rem;
}

.live-tutor-state {
  margin-bottom: 0.45rem;
  font-family: var(--sans);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--muted);
}

.live-tutor-response {
  margin: 0;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  font: 0.98rem/1.55 var(--serif);
  color: var(--ink);
  background: transparent;
}

@media (max-width: 980px) {
  .shell {
    grid-template-columns: 1fr;
  }

  .rail,
  .context {
    border: 0;
    border-bottom: 1px solid var(--rule);
  }

  .workspace {
    padding: 1rem;
  }

  .nav .uri,
  .header-meta {
    width: 100%;
    margin-left: 0;
  }
}

@media (max-width: 620px) {
  .masthead,
  .nav {
    padding-left: 1rem;
    padding-right: 1rem;
  }

  .brand small {
    display: block;
    margin-left: 0;
    margin-top: 0.2rem;
  }

  .lesson-scroll {
    padding: 1rem;
  }
}

/* Experiment 3 generated learner-shell bundle. */