:root {
  --board: #1f3a2e;       /* chalkboard green */
  --board-dark: #16281f;
  --chalk: #f4f1e8;       /* chalk white */
  --paper: #fbfaf5;
  --marker-yellow: #ffc738;
  --marker-blue: #4a90d9;
  --marker-coral: #e1523d;
  --ink: #20232b;
  --line: rgba(244, 241, 232, 0.16);

  --font-display: "Baloo 2", "Be Vietnam Pro", sans-serif;
  --font-body: "Be Vietnam Pro", system-ui, sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: var(--font-body);
  background: var(--paper);
  color: var(--ink);
  line-height: 1.5;
}

a { color: inherit; }

/* ---------- Hero / chalkboard header ---------- */
.board {
  background: radial-gradient(circle at 20% 20%, #24422f, var(--board) 60%);
  color: var(--chalk);
  padding: 64px 24px 88px;
  position: relative;
  overflow: hidden;
}

.board::after {
  /* chalk dust texture, subtle */
  content: "";
  position: absolute;
  inset: 0;
  background-image: radial-gradient(rgba(244,241,232,0.04) 1px, transparent 1px);
  background-size: 14px 14px;
  pointer-events: none;
}

.board-inner {
  max-width: 960px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.eyebrow {
  font-family: var(--font-display);
  font-size: 0.85rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--marker-yellow);
  margin: 0 0 12px;
}

h1.title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  margin: 0 0 16px;
  max-width: 14ch;
}

.subtitle {
  font-size: 1.1rem;
  max-width: 52ch;
  color: rgba(244,241,232,0.85);
  margin: 0;
}

/* ---------- Binder tabs (grade selector) ---------- */
.tabs {
  max-width: 960px;
  margin: -56px auto 64px;
  padding: 0 24px;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 16px;
  position: relative;
  z-index: 2;
}

.tab {
  background: var(--chalk);
  border-radius: 14px;
  padding: 20px 18px 22px;
  text-decoration: none;
  color: var(--ink);
  box-shadow: 0 10px 24px rgba(22, 40, 31, 0.18);
  border-top: 6px solid var(--tab-color, var(--marker-blue));
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  display: block;
}

.tab:hover, .tab:focus-visible {
  transform: translateY(-4px);
  box-shadow: 0 14px 28px rgba(22, 40, 31, 0.24);
  outline: none;
}

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

.tab-number {
  font-family: var(--font-display);
  font-size: 0.8rem;
  letter-spacing: 0.08em;
  color: var(--tab-color, var(--marker-blue));
  margin: 0 0 6px;
  font-weight: 700;
}

.tab-label {
  font-family: var(--font-display);
  font-size: 1.4rem;
  font-weight: 700;
  margin: 0 0 4px;
}

.tab-desc {
  font-size: 0.88rem;
  color: #555;
  margin: 0;
}

/* ---------- Section: about / credibility ---------- */
.about {
  max-width: 720px;
  margin: 0 auto 80px;
  padding: 0 24px;
  text-align: center;
}

.about h2 {
  font-family: var(--font-display);
  font-size: 1.6rem;
}

.about p {
  color: #4a4a4a;
}

/* ---------- Grade page ---------- */
.grade-header {
  padding: 40px 24px 8px;
  max-width: 960px;
  margin: 0 auto;
}

.back-link {
  display: inline-block;
  margin-bottom: 16px;
  font-size: 0.9rem;
  color: var(--marker-blue);
  text-decoration: none;
}
.back-link:hover { text-decoration: underline; }

.grade-header h1 {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  margin: 0 0 8px;
}

.game-grid {
  max-width: 960px;
  margin: 24px auto 80px;
  padding: 0 24px;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 20px;
}

.game-card {
  background: var(--chalk);
  border: 1px solid #e6e2d4;
  border-radius: 14px;
  padding: 22px;
  text-decoration: none;
  color: var(--ink);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.game-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 24px rgba(0,0,0,0.08);
}

.game-card h3 {
  font-family: var(--font-display);
  margin: 0 0 6px;
}

.game-card p {
  margin: 0;
  font-size: 0.9rem;
  color: #666;
}

.empty-state {
  max-width: 960px;
  margin: 24px auto 80px;
  padding: 32px 24px;
  text-align: center;
  color: #777;
  border: 1px dashed #ccc;
  border-radius: 14px;
}

footer {
  text-align: center;
  padding: 24px;
  font-size: 0.8rem;
  color: #999;
}

@media (prefers-reduced-motion: reduce) {
  .tab, .game-card { transition: none; }
}