#reaction-game {
    text-align: center;
    margin: 20px auto;
}
#game-area {
    position: relative;
    width: 300px;
    height: 300px;
    margin: 20px auto;
    background: #f0f0f0;
    border: 2px solid #ccc;
    border-radius: 10px;
}
.circle {
    position: absolute;
    width: 50px;
    height: 50px;
    background-color: #3498db;
    border-radius: 50%;
    cursor: pointer;
}
#start-btn {
    padding: 10px 20px;
    font-size: 18px;
    cursor: pointer;
}
#result {
    font-size: 20px;
    margin-top: 15px;
}