* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Trebuchet MS", "Segoe UI", sans-serif;
  color: #e2e8f0;
  background: linear-gradient(180deg, #1c1917, #0f172a 50%, #111827);
}

.top { text-align: center; padding: 1.2rem 1rem 0.4rem; }
.top h1 { margin: 0.3rem 0; color: #facc15; }
.back { color: #94a3b8; text-decoration: none; }
#meta { color: #cbd5e1; }

#board {
  max-width: 520px;
  margin: 1rem auto 2rem;
  padding: 0 1rem;
}

.card {
  background: #0f172a;
  border: 1px solid #334155;
  border-radius: 16px;
  padding: 1rem;
}

.card h2 { margin: 0 0 0.3rem; color: #fde68a; }
.note { color: #94a3b8; }

.sum-row, .seq {
  display: flex;
  gap: 0.5rem;
  align-items: center;
  margin: 0.55rem 0;
}

input[type="text"], input[type="number"] {
  border: 1px solid #475569;
  background: #020617;
  color: #f8fafc;
  border-radius: 8px;
  padding: 0.45rem 0.6rem;
  font: inherit;
  width: 7rem;
}

.colors { display: flex; gap: 0.6rem; flex-wrap: wrap; margin: 0.8rem 0; }
.swatch {
  width: 64px;
  height: 64px;
  border-radius: 12px;
  border: 3px solid transparent;
  cursor: pointer;
}
.swatch.picked { border-color: #f8fafc; }

button.go {
  margin-top: 0.8rem;
  border: 0;
  border-radius: 10px;
  padding: 0.7rem 1.2rem;
  background: #facc15;
  color: #422006;
  font: inherit;
  font-weight: 800;
  cursor: pointer;
}

.err { color: #fda4af; }
.ok { color: #86efac; font-weight: 800; }
.letters { font-size: 1.6rem; letter-spacing: 0.25rem; color: #f8fafc; }
.count-text { font-size: 1.4rem; letter-spacing: 0.2rem; }