* {
  margin: 0;
  box-sizing: border-box;
}

body {
  font-family: Arial, sans-serif;
  background: #007bff;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 20px;
}

.quiz-container {
  background: #fff;
  padding: 20px;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.8);
  width: 100%;
  max-width: 500px;
  text-align: center;
}

.btn-nivel, 
.btn-voltar, 
.btn-reiniciar {
  padding: 12px 24px;
  font-size: 1.1em;
  border: none;
  border-radius: 20px;
  margin: 10px;
  cursor: pointer;
  transition: background 0.3s ease, transform 0.2s ease;
}

.btn-nivel {
  background: #007bff;
  color: #fff;
}

.btn-nivel:hover {
  background: #0044f2;
}

.btn-voltar {
  background: #00796b;
  color: #fff;
}

.btn-voltar:hover {
  background: #e64a19;
}

.btn-reiniciar {
  background: #0044f2;
  color: #fff;
}

.btn-reiniciar:hover {
  background: #0033cc;
}

label {
  display: block;
  margin: 10px 0;
  padding: 12px;
  border-radius: 8px;
  background: #f9f9f9;
  text-align: left;
  font-size: 1.1em;
}

#tempo {
  margin: 10px 0;
  font-weight: bold;
  font-size: 1.2em;
}

h2 {
  color: #00796b;
  font-size: 1.8em;
}

@media (max-width: 600px) {
  .btn-nivel, .btn-voltar, .btn-reiniciar {
    width: 100%;
    font-size: 1em;
    padding: 10px 16px;
  }

  h2 {
    font-size: 1.6em;
  }
}

@media (max-width: 400px) {
  .btn-nivel, .btn-voltar, .btn-reiniciar {
    font-size: 0.9em;
    padding: 8px 12px;
  }

  h2 {
    font-size: 1.4em;
  }
}