* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Arial', sans-serif;
}

body {
    background-color: #f5f5f5;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 1rem;
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

h1 {
    text-align: center;
    margin-bottom: 2rem;
    color: #2c3e50;
}

.card-container {
    perspective: 1000px;
    height: 250px;
    margin-bottom: 2rem;
}

.card {
    width: 100%;
    height: 100%;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s;
}

.card.flipped {
    transform: rotateY(180deg);
}

.card-front, .card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.card-front {
    background-color: #3498db;
    color: white;
}

.card-back {
    background-color: #2ecc71;
    color: white;
    transform: rotateY(180deg);
}

.question, .answer {
    font-size: 1.5rem;
    text-align: center;
}

.buttons {
    margin-bottom: 2rem;
    text-align: center;
}

button {
    background-color: #3498db;
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 4px;
    cursor: pointer;
    font-size: 1rem;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #2980b9;
}

.rating-buttons {
    margin-top: 1rem;
}

.rating-btn {
    margin: 0.5rem 0.25rem;
    font-size: 0.9rem;
    padding: 0.5rem 1rem;
}

.rating-btn[data-rating="1"] { background-color: #e74c3c; }
.rating-btn[data-rating="2"] { background-color: #e67e22; }
.rating-btn[data-rating="3"] { background-color: #f39c12; }
.rating-btn[data-rating="4"] { background-color: #27ae60; }
.rating-btn[data-rating="5"] { background-color: #2ecc71; }

.stats {
    text-align: center;
    margin-bottom: 1rem;
    font-size: 0.9rem;
    color: #7f8c8d;
}

.reset-btn {
    display: block;
    margin: 1rem auto;
    background-color: #e74c3c;
}

.reset-btn:hover {
    background-color: #c0392b;
}