:root {
  --azul: #2563eb;
  --azul-escuro: #1d4ed8;
  --amarelo: #fbbf24;
  --verde: #22c55e;
  --roxo: #8b5cf6;
  --fundo: #f0f7ff;
  --texto: #1e293b;
  --branco: #ffffff;
  --sombra: 0 6px 16px rgba(30, 64, 175, 0.12);
  --raio: 20px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Segoe UI", "Trebuchet MS", Verdana, Arial, sans-serif;
  background: var(--fundo);
  color: var(--texto);
}

header.topo {
  background: linear-gradient(135deg, var(--azul), var(--roxo));
  color: var(--branco);
  padding: 40px 20px 60px;
  text-align: center;
}

header.topo h1 {
  font-size: 2.4rem;
  margin: 0 0 8px;
}

header.topo p {
  font-size: 1.15rem;
  margin: 0;
  opacity: 0.95;
}

main {
  max-width: 1100px;
  margin: -30px auto 60px;
  padding: 0 20px;
}

.filtros {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
  background: var(--branco);
  padding: 16px;
  border-radius: var(--raio);
  box-shadow: var(--sombra);
  margin-bottom: 30px;
}

.filtro-btn {
  border: none;
  background: var(--fundo);
  color: var(--azul-escuro);
  font-weight: 700;
  font-size: 1rem;
  padding: 10px 20px;
  border-radius: 999px;
  cursor: pointer;
  transition: transform 0.15s ease, background 0.15s ease;
}

.filtro-btn:hover { transform: translateY(-2px); }

.filtro-btn.ativo {
  background: var(--azul);
  color: var(--branco);
}

.grade {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 22px;
}

.card {
  background: var(--branco);
  border-radius: var(--raio);
  box-shadow: var(--sombra);
  padding: 22px;
  text-align: center;
  text-decoration: none;
  color: var(--texto);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  border: 3px solid transparent;
}

.card:hover {
  transform: translateY(-4px);
  border-color: var(--amarelo);
}

.card .icone {
  font-size: 3rem;
  line-height: 1;
}

.card .materia {
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.05em;
  color: var(--roxo);
  text-transform: uppercase;
}

.card h3 {
  margin: 2px 0 0;
  font-size: 1.2rem;
}

.card .nivel {
  font-size: 0.85rem;
  color: #64748b;
}

.card .jogar {
  margin-top: 10px;
  background: var(--verde);
  color: var(--branco);
  font-weight: 700;
  padding: 8px 22px;
  border-radius: 999px;
}

.vazio {
  text-align: center;
  color: #64748b;
  padding: 40px;
  font-size: 1.1rem;
}

footer {
  text-align: center;
  padding: 24px;
  color: #64748b;
  font-size: 0.9rem;
}