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

.container {
    text-align: center;
    background: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

h1 {
    color: #333;
}

.score-area {
    margin-bottom: 20px;
    font-size: 18px;
    font-weight: bold;
    color: #555;
}

.problem-description {
    margin-bottom: 20px;
    font-size: 16px;
    color: #777;
}

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

.number-container {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 20px;
}

.number-item {
    width: 60px;
    height: 60px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 24px;
    font-weight: bold;
    border: 2px solid #ccc;
    border-radius: 50%;
    color: #555;
    background-color: #e9e9e9;
    box-sizing: border-box;
}

.number-item.hidden {
    background-color: #fff;
    border: 2px dashed #999;
}

.number-item input {
    width: 100%;
    height: 100%;
    border: none;
    text-align: center;
    font-size: 24px;
    font-weight: bold;
    background: none;
    outline: none;
    padding: 0;
    box-sizing: border-box;
}

.input-area {
    display: flex;
    justify-content: center;
    gap: 10px;
}

button {
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
    border: none;
    border-radius: 5px;
    color: white;
    transition: background-color 0.3s;
}

#check-button {
    background-color: #4CAF50;
}

#check-button:hover {
    background-color: #45a049;
}

#next-button {
    background-color: #008CBA;
}

#next-button:hover {
    background-color: #007bb5;
}

.message {
    margin-top: 20px;
    font-size: 18px;
    font-weight: bold;
    min-height: 25px;
}

.message.correct {
    color: #4CAF50;
}

.message.incorrect {
    color: #f44336;
}