body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--background-color);
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 20px;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

h1 {
    font-weight: 600;
}

button {
    padding: 10px 20px;
    margin: 5px;
    cursor: pointer;
    border: none;
    border-radius: 25px;
    background-color: var(--button-background);
    color: var(--button-text);
    font-size: 16px;
    transition: background-color 0.3s, color 0.3s;
}

input[type="text"] {
    width: calc(100% - 20px);
    padding: 10px;
    margin: 10px 0;
    border: 1px solid var(--input-border);
    border-radius: 25px;
    background-color: var(--input-background);
    color: var(--input-text);
    font-size: 16px;
    transition: background-color 0.3s, color 0.3s;
}

.card {
    border: 1px solid var(--card-border);
    padding: 20px;
    margin: 20px 0;
    border-radius: 25px;
    background-color: var(--card-background);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    transition: background-color 0.3s, border-color 0.3s;
}

.question-text {
    font-size: 24px;
    font-weight: bold;
    text-align: center;
}

.button-group {
    display: flex;
    justify-content: center;
}

.hidden {
    display: none;
}

#feedback {
    margin: 10px 0;
    font-size: 18px;
    text-align: center;
}

#userAnswer {
    text-align: center;
}

/* Light Theme */
:root {
    --background-color: #f7f7f7;
    --text-color: #333;
    --button-background: #007bff;
    --button-text: #ffffff;
    --input-border: #ced4da;
    --input-background: #ffffff;
    --input-text: #495057;
    --card-border: #ced4da;
    --card-background: #ffffff;
}

/* Dark Theme */
body.dark {
    --background-color: #121212;
    --text-color: #e0e0e0;
    --button-background: #3700b3;
    --button-text: #ffffff;
    --input-border: #424242;
    --input-background: #333333;
    --input-text: #e0e0e0;
    --card-border: #424242;
    --card-background: #333333;
}