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

.container {
    text-align: center;
    max-width: 400px;
    width: 100%;
}

.grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
    margin: 20px auto;
    width: 300px;
    height: 300px;
    background: #ccc;
    padding: 10px;
    border-radius: 8px;
}

.cell {
    background: white;
    border-radius: 4px;
    transition: background 0.2s;
}

.cell.active {
    background: #007bff; /* 青く光らせる */
}

.controls {
    display: flex;
    justify-content: space-between;
    margin-bottom: 20px;
}

.game-btn {
    width: 45%;
    padding: 15px;
    font-size: 16px;
    cursor: pointer;
    background: #eee;
    border: 2px solid #aaa;
    border-radius: 8px;
}

.game-btn:active {
    background: #ddd;
    transform: translateY(2px);
}

.start-btn {
    padding: 10px 30px;
    font-size: 18px;
    cursor: pointer;
    background: #28a745;
    color: white;
    border: none;
    border-radius: 5px;
}