body {
    font-family: Arial, sans-serif;
    background: #1a1a2e;
    color: white;
    text-align: center;
    margin: 0;
    padding: 0;
}

header h1 {
    font-size: 2.5rem;
    margin: 20px 0 10px;
}

header h2 {
    font-size: 1.5rem;
    margin-bottom: 30px;
    color: #a0e7e5;
}

#quiz-container {
    max-width: 600px;
    margin: auto;
    padding: 20px;
    background: #162447;
    border-radius: 12px;
}

.options button {
    display: block;
    margin: 10px auto;
    padding: 10px 20px;
    font-size: 1rem;
    border-radius: 8px;
    border: none;
    cursor: pointer;
    background: #1f305e;
    color: white;
    transition: background 0.3s;
}

.options button:hover {
    background: #3a3f7a;
}

#progress {
    margin-top: 10px;
    font-weight: bold;
}

.ads-container {
    margin: 20px 0;
}

#leaderboard {
    margin-top: 20px;
}

#leaderboard input {
    padding: 8px;
    border-radius: 6px;
    border: none;
}

#leaderboard button {
    padding: 8px 12px;
    margin-left: 5px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
}

#leaderboard ul {
    list-style-type: none;
    padding: 0;
    margin-top: 10px;
}

/* Shake animation for wrong answer */
@keyframes shake {
  0% { transform: translateX(0); }
  25% { transform: translateX(-5px); }
  50% { transform: translateX(5px); }
  75% { transform: translateX(-5px); }
  100% { transform: translateX(0); }
}

.shake {
  animation: shake 0.5s;
}