body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f0f0f0;
    font-family: sans-serif;
    margin: 0;
}

#game-container {
    text-align: center;
    background: white;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

#puzzle-grid {
    width: 300px; /* 50px * 6 = 300px */
    height: 300px;
    display: grid;
    grid-template-columns: repeat(6, 1fr); /* 6列 */
    grid-template-rows: repeat(6, 1fr);    /* 6行 */
    border: 3px solid #333;
    margin: 20px auto;
}

.piece {
    width: 50px;
    height: 50px;
    box-sizing: border-box;
    border: 1px solid #ccc;
    background-image: url('icon.png');
    background-size: 300px 300px; /* 元の画像サイズ */
    cursor: pointer;
    transition: transform 0.2s; /* アニメーション用 */
}

.piece:hover {
    opacity: 0.8;
}

#message {
    font-size: 1.5em;
    color: green;
    font-weight: bold;
}