body {
    font-family: Arial, sans-serif;
    background-color: #f0f0f0;
    margin: 0;
    padding: 0;
}

.container {
    max-width: 800px;
    margin: 20px auto;
    padding: 20px;
    background-color: #fff;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

h1 {
    text-align: center;
}

.game-container {
    text-align: center;
    margin-top: 20px;
}

.equation {
    font-size: 24px;
    margin-bottom: 20px;
}

#user-answer {
    padding: 8px;
    font-size: 16px;
    margin-right: 10px;
}

#submit-btn {
    padding: 8px 20px;
    font-size: 16px;
    cursor: pointer;
    background-color: #4CAF50;
    color: white;
    border: none;
    border-radius: 4px;
}

#submit-btn:hover {
    background-color: #45a049;
}

.score-container {
    text-align: center;
    margin-top: 20px;
}

.rank-images-container {
    display: flex;
    justify-content: space-between;
    margin-top: 20px;
}

.rank-image {
    width: 20%; /* Adjust the width as needed */
    height: auto;
}

.popup {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.2);
    z-index: 1000;
    max-width: 90%;
    max-height: 90%;
    overflow: auto;
}