:root {
  --bg: #f4f7fb;
  --card: #ffffff;
  --ink: #10203a;
  --muted: #4a5f85;
  --accent: #0d9488;
  --focus-a: #f97316;
  --focus-b: #2563eb;
  --ray: #facc15;
  --line: #c9d5ec;
  --ok: #15803d;
  --shadow: 0 16px 32px rgba(16, 32, 58, 0.08);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f172a;
    --card: #111c33;
    --ink: #dbeafe;
    --muted: #9db4dd;
    --accent: #2dd4bf;
    --focus-a: #fb923c;
    --focus-b: #60a5fa;
    --ray: #fde047;
    --line: #274272;
    --ok: #4ade80;
    --shadow: 0 16px 32px rgba(0, 0, 0, 0.35);
  }
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  background:
    radial-gradient(circle at 8% -5%, rgba(45, 212, 191, 0.12), transparent 30%),
    radial-gradient(circle at 90% 110%, rgba(37, 99, 235, 0.12), transparent 35%),
    var(--bg);
  color: var(--ink);
  font-family: "Avenir Next", "Segoe UI", "Helvetica Neue", sans-serif;
  line-height: 1.45;
}

a {
  color: var(--accent);
  text-decoration-thickness: 2px;
}

a:focus-visible,
button:focus-visible,
input:focus-visible,
summary:focus-visible,
canvas:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 65%, #fff);
  outline-offset: 2px;
}

.container {
  width: min(1120px, 92vw);
  margin: 0 auto;
  padding: 1.25rem 0 3.25rem;
}

.hero {
  margin: 0.5rem 0 1.25rem;
}

h1,
h2,
h3 {
  margin: 0.35rem 0 0.65rem;
  line-height: 1.15;
}

h1 {
  font-size: clamp(1.8rem, 3.5vw, 2.8rem);
}

h2 {
  font-size: clamp(1.3rem, 2.1vw, 1.9rem);
}

p,
li {
  color: var(--muted);
}

.grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 1rem;
}

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

.card {
  background: var(--card);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  border-radius: 16px;
  padding: 1rem;
}

.canvas-wrap {
  width: 100%;
  height: min(62vh, 520px);
  border: 1px solid var(--line);
  border-radius: 12px;
  overflow: hidden;
  background: #0b1221;
}

canvas,
svg {
  width: 100%;
  height: 100%;
  display: block;
  touch-action: none;
}

.controls {
  display: grid;
  gap: 0.75rem;
}

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

.control-row {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 0.65rem;
}

.control-row input[type="range"] {
  width: 100%;
}

.pill {
  font-weight: 600;
  color: var(--ink);
  background: color-mix(in srgb, var(--accent) 16%, var(--card));
  border: 1px solid color-mix(in srgb, var(--accent) 35%, var(--line));
  padding: 0.2rem 0.5rem;
  border-radius: 999px;
  min-width: 4rem;
  text-align: center;
}

button,
.toggle {
  appearance: none;
  border: 1px solid var(--line);
  background: linear-gradient(145deg, color-mix(in srgb, var(--card) 80%, #fff), var(--card));
  color: var(--ink);
  border-radius: 10px;
  padding: 0.5rem 0.7rem;
  cursor: pointer;
  font: inherit;
}

button:hover,
.toggle:hover {
  border-color: var(--accent);
}

.nav-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.8rem;
}

.nav-card {
  display: block;
  border-radius: 14px;
  padding: 0.9rem;
  background: var(--card);
  border: 1px solid var(--line);
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow);
}

.nav-card h3 {
  margin: 0;
}

.nav-card p {
  margin: 0.4rem 0 0;
  font-size: 0.95rem;
}

.legend {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  font-size: 0.92rem;
}

.legend span {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}

.swatch {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.kpi {
  margin: 0;
  font-size: 0.96rem;
  color: var(--ink);
}

.note {
  font-size: 0.9rem;
}

.spaced {
  margin-top: 1rem;
}

.teach-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.8rem;
}

.teach-card {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 0.8rem;
  background: color-mix(in srgb, var(--card) 88%, var(--accent) 5%);
}

.teach-card h3 {
  font-size: 1rem;
  margin-bottom: 0.35rem;
}

.teach-card p,
.teach-card li {
  margin: 0.25rem 0;
  font-size: 0.92rem;
}

.teach-card ul {
  margin: 0.35rem 0 0;
  padding-left: 1rem;
}

header.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.8rem;
}

header.site-header nav {
  display: flex;
  gap: 0.6rem;
  flex-wrap: wrap;
}

header.site-header nav a {
  text-decoration: none;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.3rem 0.65rem;
  color: var(--ink);
  background: color-mix(in srgb, var(--card) 88%, #fff);
}

@media (max-width: 560px) {
  .container {
    width: min(100% - 1rem, 1120px);
    padding-top: 0.75rem;
  }

  .card {
    border-radius: 12px;
    padding: 0.8rem;
  }

  .canvas-wrap {
    height: min(58vh, 420px);
  }

  .control-row {
    grid-template-columns: 1fr auto;
  }

  .control-row input[type="range"] {
    grid-column: 1 / -1;
    min-height: 2.4rem;
  }

  .button-row button {
    min-height: 2.5rem;
  }
}

.debug-panel {
  margin-top: 0.8rem;
  border: 1px dashed color-mix(in srgb, var(--accent) 60%, var(--line));
  border-radius: 10px;
  padding: 0.45rem 0.65rem;
  background: color-mix(in srgb, var(--card) 80%, var(--accent) 6%);
}

.debug-panel summary {
  cursor: pointer;
  font-weight: 600;
}

.debug-controls {
  margin-top: 0.45rem;
  display: grid;
  gap: 0.45rem;
}

.debug-controls button {
  width: fit-content;
}

.debug-hint {
  margin: 0;
  font-size: 0.85rem;
}

table.inline-math {
  width: 100%;
  border-collapse: collapse;
}

table.inline-math td,
table.inline-math th {
  border: 1px solid var(--line);
  padding: 0.35rem 0.5rem;
  font-size: 0.92rem;
}

.progress-strip {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin: 0 0 0.8rem;
  padding: 0.45rem 0.85rem;
  background: color-mix(in srgb, var(--card) 92%, var(--accent) 6%);
  border: 1px solid var(--line);
  border-radius: 18px;
  font-size: 0.85rem;
  color: var(--muted);
}

.progress-strip .progress-label {
  font-weight: 600;
  color: var(--ink);
  white-space: nowrap;
}

.progress-strip .progress-dots {
  display: flex;
  gap: 0.3rem;
  flex-wrap: wrap;
  margin-left: auto;
}

.progress-strip .progress-dot {
  width: 1.55rem;
  height: 1.55rem;
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.78rem;
  font-weight: 600;
  background: color-mix(in srgb, var(--card) 80%, var(--line));
  color: var(--muted);
  text-decoration: none;
  border: 1px solid var(--line);
}

.progress-strip .progress-dot:hover,
.progress-strip .progress-dot:focus-visible {
  border-color: var(--accent);
  color: var(--ink);
}

.progress-strip .progress-dot[aria-current="page"] {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.start-here {
  border: 1px solid color-mix(in srgb, var(--focus-a) 55%, var(--line));
  background: color-mix(in srgb, var(--focus-a) 10%, var(--card));
  border-radius: 12px;
  padding: 0.6rem 0.8rem;
  margin: 0 0 0.2rem;
}

.start-here h3 {
  font-size: 0.92rem;
  margin: 0 0 0.25rem;
  color: var(--ink);
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.start-here h3::before {
  content: "▶";
  color: var(--focus-a);
  font-size: 0.7rem;
  line-height: 1;
}

.start-here p {
  margin: 0;
  color: var(--ink);
  font-size: 0.92rem;
}

.drag-hint {
  margin: 0.4rem 0 0;
  padding: 0.35rem 0.6rem;
  font-size: 0.85rem;
  color: var(--muted);
  font-style: italic;
  border-left: 3px solid color-mix(in srgb, var(--accent) 55%, var(--line));
  background: color-mix(in srgb, var(--accent) 5%, transparent);
  border-radius: 4px;
}

.look-for {
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0.45rem 0 0.1rem;
}

.objective-tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  padding: 0.12rem 0.5rem;
  border-radius: 999px;
  background: color-mix(in srgb, var(--accent) 16%, var(--card));
  color: var(--ink);
  border: 1px solid color-mix(in srgb, var(--accent) 40%, var(--line));
  margin-bottom: 0.35rem;
}

.student-tip {
  background: color-mix(in srgb, var(--focus-b) 8%, var(--card));
  border: 1px solid color-mix(in srgb, var(--focus-b) 45%, var(--line));
}

.student-tip h2 {
  margin-bottom: 0.3rem;
}

.student-tip ol {
  margin: 0.4rem 0 0;
  padding-left: 1.2rem;
  color: var(--ink);
}

.student-tip ol li {
  margin: 0.25rem 0;
  color: var(--ink);
}

.cta-row {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-top: 0.7rem;
}

.cta-primary {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.6rem 1rem;
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  text-decoration: none;
  font-weight: 600;
  border: 1px solid var(--accent);
}

.cta-primary:hover,
.cta-primary:focus-visible {
  filter: brightness(1.08);
}

.cta-secondary {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.6rem 1rem;
  border-radius: 10px;
  border: 1px solid var(--line);
  color: var(--ink);
  text-decoration: none;
  background: var(--card);
}

.teacher-actions {
  border-top: 1px dashed var(--line);
  margin-top: 0.4rem;
  padding-top: 0.55rem;
}

.teacher-actions-label {
  display: block;
  font-size: 0.74rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.35rem;
}

@media (max-width: 560px) {
  .progress-strip {
    font-size: 0.78rem;
    padding: 0.35rem 0.55rem;
    gap: 0.35rem;
  }

  .progress-strip .progress-dot {
    width: 1.4rem;
    height: 1.4rem;
    font-size: 0.72rem;
  }
}