:root {
  --brand-navy: #041E42;
  --brand-red: #D50032;
  --brand-teal: #007288;
  --page: #F6F8FB;
  --surface: #FFFFFF;
  --surface-soft: #EEF3F8;
  --text: #182B42;
  --muted: #526174;
  --border: #DCE3EC;
  --focus: #007288;
  --success: #246044;
  --warning: #855200;
  --error: #AE1834;
  --radius-card: 18px;
  --radius-control: 10px;
  --shadow-card: 0 8px 28px rgba(4, 30, 66, 0.06);
  --space: 24px;
  --space-sm: 16px;
  --header-h: 72px;
  --max: 1180px;
  --measure: 70ch;
  --font: system-ui, "Segoe UI", sans-serif;
  --transition: 150ms ease;
}

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

html {
  font-size: 16px;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font);
  color: var(--text);
  background:
    radial-gradient(1200px 500px at 10% -10%, rgba(0, 114, 136, 0.08), transparent 55%),
    radial-gradient(900px 420px at 100% 0%, rgba(213, 0, 50, 0.05), transparent 50%),
    var(--page);
  line-height: 1.6;
}

img {
  max-width: 100%;
  height: auto;
}

a {
  color: var(--brand-teal);
}

a:hover {
  color: var(--brand-navy);
}

:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--surface);
  color: var(--text);
  padding: 0.75rem 1rem;
  z-index: 1000;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
}

.app-header__inner {
  width: min(100% - 2 * var(--space), var(--max));
  margin-inline: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  text-decoration: none;
  color: inherit;
}

.brand__name {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--brand-navy);
  letter-spacing: -0.02em;
}

.brand__name::after {
  content: "";
  display: inline-block;
  width: 0.45rem;
  height: 0.45rem;
  margin-left: 0.4rem;
  border-radius: 50%;
  background: var(--brand-red);
  vertical-align: middle;
}

.brand__meta {
  font-size: 0.8rem;
  color: var(--muted);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.35rem 0.7rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface-soft);
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 600;
}

.badge--live {
  border-color: rgba(36, 96, 68, 0.35);
  color: var(--success);
  background: #eef7f1;
}

.badge--fixture {
  border-color: rgba(133, 82, 0, 0.35);
  color: var(--warning);
  background: #fff7ea;
}

.badge--error {
  border-color: rgba(174, 24, 52, 0.35);
  color: var(--error);
  background: #fff0f3;
}

.main {
  width: min(100% - 2 * var(--space), var(--max));
  margin: 2rem auto 3rem;
}

.hero {
  max-width: 42rem;
  margin-bottom: 2rem;
}

.hero h1 {
  margin: 0 0 0.75rem;
  color: var(--brand-navy);
  font-size: clamp(1.8rem, 3vw, 2.4rem);
  line-height: 1.2;
  letter-spacing: -0.02em;
}

.hero p {
  margin: 0;
  color: var(--muted);
  font-size: 1.05rem;
}

.choice-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.25rem;
}

.choice-card {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
  padding: 1.6rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-card);
  text-decoration: none;
  color: inherit;
  transition: transform var(--transition), border-color var(--transition), box-shadow var(--transition);
}

.choice-card:hover {
  transform: translateY(-2px);
  border-color: #c5d3e2;
  box-shadow: 0 12px 32px rgba(4, 30, 66, 0.08);
}

.choice-card h2 {
  margin: 0;
  color: var(--brand-navy);
  font-size: 1.35rem;
}

.choice-card p {
  margin: 0;
  color: var(--muted);
  flex: 1;
}

.choice-card__cta {
  color: var(--brand-teal);
  font-weight: 600;
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-card);
  padding: 1.5rem;
}

.panel + .panel {
  margin-top: 1.25rem;
}

.panel h2,
.panel h3 {
  margin-top: 0;
  color: var(--brand-navy);
}

.muted {
  color: var(--muted);
}

.small {
  font-size: 0.9rem;
}

.stack {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
}

label,
.field-label {
  display: block;
  font-weight: 600;
  color: var(--brand-navy);
  margin-bottom: 0.35rem;
}

.field-hint {
  display: block;
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 0.35rem;
}

textarea,
input[type="text"],
input[type="number"],
select {
  width: 100%;
  font: inherit;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-control);
  padding: 0.75rem 0.9rem;
}

textarea {
  min-height: 7rem;
  resize: vertical;
  line-height: 1.55;
}

textarea:focus,
input:focus,
select:focus {
  border-color: var(--focus);
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.chip {
  appearance: none;
  border: 1px solid var(--border);
  background: var(--surface-soft);
  color: var(--text);
  border-radius: 999px;
  padding: 0.45rem 0.85rem;
  font: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition);
}

.chip:hover,
.chip[aria-pressed="true"] {
  background: #e4eef5;
  border-color: #b7c9da;
}

.btn {
  appearance: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  border-radius: var(--radius-control);
  border: 1px solid transparent;
  padding: 0.7rem 1.1rem;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}

.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.btn--primary {
  background: var(--brand-navy);
  color: #fff;
}

.btn--primary:hover:not(:disabled) {
  background: #0a2f5c;
}

.btn--secondary {
  background: var(--surface);
  color: var(--brand-navy);
  border-color: var(--border);
}

.btn--secondary:hover:not(:disabled) {
  background: var(--surface-soft);
}

.btn--teal {
  background: var(--brand-teal);
  color: #fff;
}

.btn--teal:hover:not(:disabled) {
  background: #006277;
}

.btn--danger {
  background: #fff;
  color: var(--error);
  border-color: #f0c2cb;
}

.btn--danger:hover:not(:disabled) {
  background: #fff0f3;
}

.dropzone {
  border: 1.5px dashed #b8c7d8;
  border-radius: var(--radius-card);
  background: var(--surface-soft);
  padding: 1.25rem;
  text-align: center;
}

.dropzone[data-active="true"] {
  border-color: var(--brand-teal);
  background: #e7f4f6;
}

.defaults {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.workspace {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 300px;
  gap: 1.25rem;
  align-items: start;
}

.conversation {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  max-width: var(--measure);
}

.turn {
  padding: 0.9rem 1rem;
  border-radius: 14px;
  border: 1px solid transparent;
}

.turn--tutor {
  background: transparent;
  border-color: transparent;
  padding-left: 0;
  padding-right: 0;
}

.turn--learner {
  background: #eaf2f8;
  border-color: #d5e3ef;
}

.turn--system {
  background: var(--surface-soft);
  color: var(--muted);
  font-size: 0.92rem;
}

.turn__meta {
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.35rem;
}

.turn__body {
  font-size: 1.0625rem;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}

.composer {
  margin-top: 1rem;
}

.composer textarea {
  min-height: 5.5rem;
  max-height: 12rem;
}

.composer__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
  justify-content: space-between;
  margin-top: 0.75rem;
}

.rail {
  position: sticky;
  top: calc(var(--header-h) + 1rem);
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.rail details {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-card);
  padding: 1rem;
}

.rail summary {
  cursor: pointer;
  font-weight: 700;
  color: var(--brand-navy);
}

.fact-list {
  margin: 0.75rem 0 0;
  padding-left: 1.1rem;
  color: var(--text);
}

.fact-list li + li {
  margin-top: 0.4rem;
}

.refs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.5rem;
}

.ref-chip {
  appearance: none;
  border: 1px solid var(--border);
  background: #fff;
  color: var(--brand-teal);
  border-radius: 999px;
  padding: 0.25rem 0.6rem;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
}

.progress {
  font-weight: 700;
  color: var(--brand-navy);
}

.alert {
  border-radius: var(--radius-control);
  padding: 0.85rem 1rem;
  border: 1px solid var(--border);
}

.alert--error {
  background: #fff0f3;
  border-color: #f0c2cb;
  color: var(--error);
}

.alert--warning {
  background: #fff7ea;
  border-color: #efd4a4;
  color: var(--warning);
}

.alert--info {
  background: #eef6f8;
  border-color: #c5e0e6;
  color: var(--brand-navy);
}

.feedback-block {
  max-width: var(--measure);
}

.feedback-block h2 {
  color: var(--brand-navy);
}

.feedback-block ul {
  padding-left: 1.2rem;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.new-message-indicator {
  position: sticky;
  bottom: 1rem;
  align-self: center;
  display: none;
}

.new-message-indicator[data-visible="true"] {
  display: inline-flex;
}

.footer-links {
  margin-top: 2rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.limitations {
  max-width: 48rem;
}

.limitations h1 {
  color: var(--brand-navy);
}

.hero-lead {
  font-size: 1.1rem;
  color: var(--text);
  max-width: 42rem;
}

.demo-panel {
  margin-top: 2.5rem;
  padding: 1.5rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-card);
}

.demo-panel__header {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 0.75rem;
}

.demo-panel__header h2 {
  margin: 0;
  color: var(--brand-navy);
}

.demo-panel__badge {
  margin: 0;
  font-size: 0.82rem;
  color: var(--warning);
  background: #fff7ea;
  border: 1px solid #efd4a4;
  border-radius: var(--radius-control);
  padding: 0.35rem 0.65rem;
}

.compare-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  margin: 1rem 0;
}

.compare-card {
  padding: 1rem;
  background: var(--surface-soft);
  border-radius: var(--radius-control);
  border: 1px solid var(--border);
}

.compare-card h3 {
  margin-top: 0;
  color: var(--brand-navy);
  font-size: 1.05rem;
}

.compare-learner {
  background: #eaf2f8;
  border-radius: 10px;
  padding: 0.75rem;
}

.compare-why {
  margin-bottom: 0;
  font-size: 0.92rem;
  color: var(--brand-teal);
}

.sample-resource {
  border-color: #b7d8df;
  background: linear-gradient(180deg, #f3fafb, #fff);
}

.sample-resource h3 {
  margin: 0 0 0.35rem;
  color: var(--brand-navy);
}

#challenge-desc {
  margin: 0;
  min-height: 2.6em;
}

body[data-busy='1'] .composer,
body[data-busy='1'] .rail .btn {
  opacity: 0.72;
}

.alert--error:focus-visible,
.btn:focus-visible,
.ref-chip:focus-visible,
.chip:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
  outline: 3px solid var(--brand-teal);
  outline-offset: 2px;
}

@media (max-width: 768px) {
  .compare-grid,
  .choice-grid,
  .workspace,
  .defaults {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 390px) {
  .hero h1 {
    font-size: 1.55rem;
  }

  .composer__actions {
    flex-direction: column;
    align-items: stretch;
  }
}

@media (max-width: 900px) {
  .compare-grid {
    grid-template-columns: 1fr;
  }

  .choice-grid,
  .workspace,
  .defaults {
    grid-template-columns: 1fr;
  }

  .rail {
    position: static;
  }

  .main {
    margin-top: 1.25rem;
    width: min(100% - 2 * var(--space-sm), var(--max));
  }

  .app-header__inner {
    width: min(100% - 2 * var(--space-sm), var(--max));
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition: none !important;
    animation: none !important;
  }
}

@media print {
  body {
    background: #fff;
  }

  .app-header,
  .composer,
  .rail,
  .btn,
  .footer-links,
  .skip-link {
    display: none !important;
  }

  .main {
    width: 100%;
    margin: 0;
  }

  .panel {
    box-shadow: none;
    border: none;
    padding: 0;
  }
}