body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f0f2f5;
}

.card-container {
    perspective: 1000px;
}

.card {
    width: 600px;
    height: 300px;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s;
    cursor: pointer;
}

.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: 10px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
    padding: 20px;
    box-sizing: border-box;
}

.card-front {
    background-color: #ffffff;
    flex-direction: column;
}

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

.hanzi {
    font-size: 30px;
    margin: 0;
}

.pinyin {
    font-size: 18px;
    color: #666;
    margin-bottom: 10px;
}

.english {
    font-size: 18px;
}

.navigation {
    position: absolute;
    bottom: 20px;
    display: flex;
    gap: 10px;
}

button {
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    background-color: #007bff;
    color: white;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #0056b3;
}

.settings {
    position: absolute;
    top: 20px;
    right: 20px;
    display: flex;
    gap: 10px;
}

#settingsBtn {
    background-color: transparent;
    border: none;
    font-size: 24px;
    cursor: pointer;
}

#installBtn {
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    background-color: #28a745;
    color: white;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
}

#installBtn:hover {
    background-color: #218838;
}