body {
    margin: 0;
    font-family: 'Arial', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: linear-gradient(to bottom, #2c3e50, #3498db);
    color: white;
}

#game-container {
    text-align: center;
}

#start-button {
    padding: 15px 30px;
    font-size: 1.5rem;
    background-color: #3498db;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    box-shadow: 0px 4px 6px rgba(0, 0, 0, 0.2);
    transition: background-color 0.3s;
}

#start-button:hover {
    background-color: #1abc9c;
}

#game-area {
    margin-top: 20px;
}

#instruction {
    margin-bottom: 10px;
    font-size: 1.2rem;
}

#game-background {
    width: 300px;
    height: 300px;
    margin: 20px auto;
    background-color: blue;
    border-radius: 15px;
    transition: background-color 0.2s;
    cursor: pointer;
}

.hidden {
    display: none;
}

#chart-container {
    margin-top: 30px;
}