:root {
  --fg: #1c1c1c;
  --muted: #6a6a6a;
  --bg: #fafafa;
  --panel: #ffffff;
  --border: #e2e2e2;
  --accent: #2b6cb0;
  --correct: #2f855a;
  --incorrect: #c53030;
  --bar: #2b6cb0;
  --bar-bg: #e2e8f0;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  color: var(--fg);
  background: var(--bg);
  font-size: 16px;
  line-height: 1.5;
}

header {
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border);
  background: var(--panel);
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}

header h1 { margin: 0; font-size: 1.25rem; }
#session-info { color: var(--muted); font-size: 0.875rem; }

main {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 1.5rem;
  padding: 1.5rem;
  max-width: 1100px;
  margin: 0 auto;
}

@media (max-width: 720px) {
  main { grid-template-columns: 1fr; }
}

section, aside {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.25rem 1.5rem;
}

#start-panel label { display: block; margin-bottom: 0.75rem; }
#start-panel input[type="text"] {
  margin-left: 0.5rem;
  padding: 0.375rem 0.625rem;
  border: 1px solid var(--border);
  border-radius: 4px;
  font-size: 1rem;
}
.reset-line { font-size: 0.875rem; color: var(--muted); }

button {
  background: var(--accent);
  color: white;
  border: none;
  padding: 0.5rem 1rem;
  border-radius: 4px;
  font-size: 0.9375rem;
  cursor: pointer;
}
button:hover { background: #1e4d7e; }
button:disabled { opacity: 0.5; cursor: not-allowed; }
#skip-btn { background: #888; margin-left: 0.5rem; }
#skip-btn:hover { background: #666; }

#kc-tag {
  display: flex;
  align-items: baseline;
  gap: 0.625rem;
  flex-wrap: wrap;
  margin-bottom: 0.625rem;
}
.kc-tag-name {
  color: var(--fg);
  font-size: 0.9375rem;
  font-weight: 600;
  line-height: 1.3;
}
.kc-tag-id {
  color: var(--muted);
  font-family: monospace;
  font-size: 0.75rem;
}
.remediation-tag {
  display: inline-block;
  margin-left: 0.5rem;
  padding: 0.125rem 0.5rem;
  background: #fef3c7;
  color: #92400e;
  border-radius: 3px;
  font-size: 0.75rem;
}

#prompt {
  font-size: 1.125rem;
  margin: 0.75rem 0 1rem;
  min-height: 2.5em;
}

#choices {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-bottom: 1rem;
}
.choice {
  padding: 0.625rem 1rem;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: #fafafa;
  cursor: pointer;
  text-align: left;
  font-size: 0.9375rem;
  color: var(--fg);
}
.choice:hover { background: #f0f0f0; }
.choice .idx { color: var(--muted); margin-right: 0.5rem; font-weight: 600; }

#answer-form {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}
#answer-input {
  flex: 1;
  padding: 0.5rem 0.75rem;
  font-size: 1rem;
  border: 1px solid var(--border);
  border-radius: 4px;
}

#feedback {
  margin-top: 1rem;
  font-size: 0.9375rem;
  min-height: 1.5em;
}
.feedback-correct { color: var(--correct); }
.feedback-incorrect { color: var(--incorrect); }
.feedback-meta { color: var(--muted); margin-left: 0.5rem; font-size: 0.875rem; }

#explanation {
  margin-top: 0.75rem;
  padding: 0.75rem 1rem;
  background: #fff8e7;
  border-left: 3px solid #d69e2e;
  border-radius: 4px;
  font-size: 0.9375rem;
  line-height: 1.5;
}
#explanation:empty { display: none; }

#feedback-lesson {
  margin-top: 0.75rem;
  padding: 1rem 1.25rem;
  background: #f3f8fd;
  border-left: 4px solid var(--accent);
  border-radius: 4px;
  font-size: 0.9375rem;
  line-height: 1.55;
}
#feedback-lesson:empty { display: none; }
#feedback-lesson .lesson-tag {
  display: inline-block;
  background: var(--accent);
  color: white;
  font-size: 0.6875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.125rem 0.5rem;
  border-radius: 3px;
  margin-bottom: 0.5rem;
}
#feedback-lesson h2,
#feedback-lesson h3 {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1.0625rem;
}
#feedback-lesson p { margin: 0.5rem 0; }
#feedback-lesson ul, #feedback-lesson ol { padding-left: 1.5rem; }

#followup-note {
  margin-top: 0.5rem;
  font-size: 0.8125rem;
  color: var(--muted);
  font-style: italic;
}
#followup-note:empty { display: none; }

.link-btn {
  background: none;
  color: var(--muted);
  border: none;
  padding: 0.5rem 0;
  margin-top: 0.75rem;
  font-size: 0.8125rem;
  text-decoration: underline;
  cursor: pointer;
}
.link-btn:hover { color: var(--fg); background: none; }

.dispute-corner,
.lesson-corner {
  position: fixed;
  bottom: 1rem;
  background: var(--panel);
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.375rem 0.75rem;
  font-size: 0.8125rem;
  cursor: pointer;
  z-index: 40;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}
.dispute-corner { left: 1rem; }
.lesson-corner  { right: 1rem; background: #e6f0fa; color: var(--accent); border-color: #b6d3ec; }
.dispute-corner:hover { color: var(--fg); background: #f5f5f5; }
.lesson-corner:hover  { background: #d3e4f5; }

/* Inline lesson card (auto-shown before an item on first encounter / reteach) */
#lesson-card {
  border-left: 4px solid var(--accent);
  background: #f3f8fd;
  border-radius: 4px;
  padding: 1rem 1.25rem;
  margin-bottom: 1.25rem;
}
#lesson-card[hidden] { display: none; }
.lesson-card-tag {
  display: inline-block;
  background: var(--accent);
  color: white;
  font-size: 0.6875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.125rem 0.5rem;
  border-radius: 3px;
  margin-bottom: 0.5rem;
}
#lesson-card-body h2,
#lesson-card-body h3,
#lesson-modal-body h2,
#lesson-modal-body h3 {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1.0625rem;
}
#lesson-card-body p,
#lesson-modal-body p { margin: 0.5rem 0; line-height: 1.55; }
#lesson-card-body ul,
#lesson-card-body ol,
#lesson-modal-body ul,
#lesson-modal-body ol { padding-left: 1.5rem; line-height: 1.55; }
#lesson-card-body code,
#lesson-modal-body code {
  background: rgba(0, 0, 0, 0.05);
  padding: 0.0625rem 0.25rem;
  border-radius: 2px;
  font-size: 0.875em;
}
#lesson-card-dismiss {
  margin-top: 0.75rem;
}

.lesson-modal-card {
  max-width: 640px;
  max-height: 80vh;
  overflow-y: auto;
}

.modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 50;
}
.modal[hidden] { display: none; }
.modal-card {
  background: var(--panel);
  border-radius: 8px;
  padding: 1.5rem;
  max-width: 480px;
  width: calc(100% - 2rem);
}
.modal-card h3 { margin: 0 0 0.5rem; }
.modal-card .muted { color: var(--muted); font-size: 0.9375rem; }
.modal-card textarea {
  width: 100%;
  margin-top: 0.5rem;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 4px;
  font: inherit;
  resize: vertical;
}
.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
  margin-top: 1rem;
}
.modal-actions #dispute-cancel { background: #888; }
.modal-actions #dispute-cancel:hover { background: #666; }
#dispute-feedback {
  margin-top: 0.5rem;
  font-size: 0.875rem;
  color: var(--correct);
  min-height: 1.25em;
}

#status-panel h3 {
  margin: 0 0 0.75rem;
  font-size: 0.9375rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
}
.status-row {
  margin-bottom: 0.625rem;
  font-size: 0.8125rem;
  cursor: help;
}
.status-row .kc-label {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 0.5rem;
  margin-bottom: 0.25rem;
}
.status-row .kc-name { line-height: 1.3; }
.status-row .kc-id {
  font-family: monospace;
  color: var(--muted);
  font-size: 0.6875rem;
  flex-shrink: 0;
}
.status-row .kc-bar {
  display: grid;
  grid-template-columns: 1fr 36px;
  gap: 0.5rem;
  align-items: center;
}
.status-row .pval {
  text-align: right;
  font-variant-numeric: tabular-nums;
  color: var(--muted);
  font-size: 0.75rem;
}

/* Per-status visual treatment. */
.status-row.status-mastered .kc-name { color: var(--correct); }
.status-row.status-mastered .bar-fill { background: var(--correct); }

.status-row.status-in_progress .bar-fill { background: var(--accent); }

.status-row.status-available .kc-name { color: var(--muted); }
.status-row.status-available .bar-fill { background: transparent; }

.status-row.status-locked .kc-name {
  color: var(--muted);
  font-style: italic;
}
.status-row.status-locked .kc-id { opacity: 0.5; }
.status-row.status-locked .bar { background: transparent; }
.status-row.status-locked .bar-fill { background: transparent; }
.status-row.status-locked .kc-name::after {
  content: " 🔒";
  font-style: normal;
  font-size: 0.6875rem;
}
.bar {
  height: 6px;
  background: var(--bar-bg);
  border-radius: 3px;
  overflow: hidden;
}
.bar-fill {
  height: 100%;
  background: var(--bar);
}
.bar-fill.mastered { background: var(--correct); }

#end-panel h2 { margin-top: 0; }
#end-panel #end-note { color: var(--muted); }

#summary-stats {
  margin: 1rem 0 1.5rem;
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  font-size: 0.9375rem;
}
#summary-stats .stat { color: var(--muted); }
#summary-stats .stat b { color: var(--fg); font-variant-numeric: tabular-nums; }

#curriculum-progress {
  margin: 1rem 0 1.25rem;
  padding: 1rem 1.25rem;
  background: #edf2f7;
  border-radius: 6px;
}
#curriculum-progress .headline {
  font-size: 1.0625rem;
  margin-bottom: 0.5rem;
}
#curriculum-progress .headline b {
  font-size: 1.25rem;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}
#curriculum-progress .bar {
  height: 10px;
  background: var(--bar-bg);
  border-radius: 5px;
  overflow: hidden;
  display: flex;
}
#curriculum-progress .bar .seg-mastered { background: var(--correct); }
#curriculum-progress .bar .seg-progress { background: var(--accent); }
#curriculum-progress .legend {
  margin-top: 0.5rem;
  font-size: 0.8125rem;
  color: var(--muted);
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}
#curriculum-progress .legend .dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 2px;
  margin-right: 0.375rem;
  vertical-align: -1px;
}
#curriculum-progress .dot.mastered { background: var(--correct); }
#curriculum-progress .dot.progress { background: var(--accent); }
#curriculum-progress .dot.not-started { background: var(--bar-bg); }

.summary-group {
  margin-bottom: 1.5rem;
}
.summary-group h3 {
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin: 0 0 0.25rem;
}
.summary-group .blurb {
  font-size: 0.9375rem;
  color: var(--muted);
  margin: 0 0 0.625rem;
}
.summary-group.mastered h3 { color: var(--correct); }
.summary-group.improved  h3 { color: var(--accent); }
.summary-group.struggling h3 { color: var(--incorrect); }
.summary-group.steady    h3 { color: var(--muted); }

.summary-row {
  display: grid;
  grid-template-columns: 1fr auto auto;
  gap: 0.75rem;
  align-items: baseline;
  padding: 0.375rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.9375rem;
}
.summary-row:last-child { border-bottom: none; }
.summary-row .name { line-height: 1.3; }
.summary-row .delta {
  font-variant-numeric: tabular-nums;
  font-size: 0.8125rem;
  color: var(--muted);
}
.summary-row .delta .up { color: var(--correct); }
.summary-row .delta .down { color: var(--incorrect); }
.summary-row .id {
  font-family: monospace;
  font-size: 0.75rem;
  color: var(--muted);
}