body {
    font-family: 'Arial', sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100vh;
    margin: 0;
    background-color: #f0f8ff; /* 淡藍色背景，柔和不刺眼 */
    color: #333;
}

h1 {
    color: #0056b3;
    margin-bottom: 20px;
}

.controls {
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 15px; /* 控制項之間的間距 */
}

select, button {
    padding: 10px 15px;
    font-size: 16px;
    border-radius: 8px;
    border: 2px solid #0056b3;
    cursor: pointer;
    background-color: #fff;
    color: #0056b3;
    font-weight: bold;
    transition: background-color 0.3s, color 0.3s;
}

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

.back-button {
    margin-top: 20px;
    padding: 12px 25px;
    font-size: 18px;
    border-radius: 8px;
    border: 2px solid #0056b3;
    cursor: pointer;
    background-color: #fff;
    color: #0056b3;
    font-weight: bold;
    text-decoration: none;
    transition: background-color 0.3s, color 0.3s;
}

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

.game-board {
    display: grid;
    gap: 10px;
    perspective: 1000px; /* 為了3D翻轉效果 */
}

.card {
    width: 100px;
    height: 100px;
    cursor: pointer;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s;
    border-radius: 10px;
}

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

.card-face {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden; /* 隱藏背面 */
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}

.card-front {
    background-color: #4a90e2; /* 卡片正面顏色 */
    font-size: 48px;
}

.card-back {
    background-color: #ffffff; /* 卡片背面顏色 */
    transform: rotateY(180deg);
    font-size: 50px; /* 汽車圖案大小 */
}

.card.matched .card-back {
    background-color: #a8e6cf; /* 配對成功後的顏色 */
    box-shadow: 0 0 15px #a8e6cf;
}

.instructions {
    margin-top: 20px;
    font-size: 18px;
    color: #555;
}