body {
    font-family: 'Roboto', Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #eaf2f8;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 800px;
    margin: 50px auto;
    padding: 20px;
    background: #ffffff;
    border-radius: 12px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
}

h1 {
    text-align: center;
    color: #333;
    font-size: 2.5em;
    margin-bottom: 20px;
}

.hidden {
    display: none;
}

button {
    padding: 12px 24px;
    background: #007bff;
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 1em;
    transition: background-color 0.3s ease;
    text-transform: uppercase;
    font-weight: bold;
}

button:hover {
    background: #0056b3;
}

button:active {
    transform: scale(0.98);
}

button:disabled {
    background: #cccccc;
    cursor: not-allowed;
}

label {
    font-weight: bold;
    display: block;
    margin-bottom: 8px;
    color: #555;
}

select {
    width: 100%;
    padding: 10px;
    font-size: 1em;
    margin-bottom: 20px;
    border: 1px solid #ccc;
    border-radius: 6px;
}

.quiz-container button {
    display: block;
    margin: 15px 0;
}

.feedback {
    margin: 20px 0;
    font-weight: bold;
    font-size: 1.2em;
    text-align: center;
    color: #444;
}

.streak {
    font-weight: bold;
    margin-top: 20px;
    font-size: 1.2em;
    color: #007bff;
}

input[type="file"] {
    margin-top: 10px;
    margin-bottom: 20px;
    font-size: 1em;
}

#lesson-selection {
    margin-bottom: 30px;
    text-align: center;
}

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

#options button {
    width: 100%;
    margin: 10px 0;
    padding: 10px;
    font-size: 1em;
    border: 1px solid #ccc;
    border-radius: 6px;
    transition: background-color 0.3s ease;
}

#options button:hover {
    background-color: #f0f8ff;
    color: #007bff;
}

.alert {
    margin: 20px 0;
    padding: 10px;
    background: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
    border-radius: 6px;
}