html {
    background: radial-gradient(circle at center, #ffffff 0%, #e0f7fa 100%);
    min-height: 100%;
}

body {
    background: transparent;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.inner {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    padding-inline: 20px;
    margin: 30px 0;
}

.page-title {
    font-size: 1.8rem;
    margin-bottom: 5px;
    text-align: center;
    position: relative;
    display: inline-block;
    font-weight: bold;
}

.page-title::before {
    content: "\1F4D6";
    /* book icon */
    margin-right: 8px;
}

.page-title::after {
    content: "";
    display: block;
    width: 50px;
    height: 3px;
    background: #4caf50;
    margin: 8px auto 0;
    border-radius: 2px;
}

.page-subtitle {
    font-size: 1.5rem;
    font-weight: bold;
    margin-bottom: 15px;
    text-align: center;
}

.title {
    font-size: 1.8rem;
    text-align: center;
    margin-bottom: 0;
}

.level-buttons {
    margin-bottom: 15px;
    display: flex;
    gap: 10px;
    justify-content: center;
}

.level-buttons button.active {
    background-color: #f57c00;
    /* background-color: #388e3c; */
    color: #fff;
}

.content {
    display: none;
}

.top-content,
.content {
    background: white;
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    text-align: center;
    width: 90%;
    height: auto;
    max-width: 350px;
    margin-bottom: 20px;
}

.content img {
    max-height: 200px;
    width: auto;
    max-width: 100%;
    height: 200px;
    margin-top: 20px;
    object-fit: contain;
    width: 100%;
    border-radius: 12px;
    margin-bottom: 10px;
}

.word {
    font-size: clamp(1.6rem, 5vw, 3rem);
    white-space: normal;
    word-wrap: break-word;
    margin-bottom: 20px;
    text-align: center;
    line-height: 1.3;
}

button {
    width: 80%;
    max-width: 300px;
    padding: 15px;
    margin: 10px 0;
    font-size: 1.2rem;
    border: none;
    border-radius: 8px;
    background-color: #4caf50;
    color: white;
}

button:active {
    background-color: #45a049;
}

.options {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.options button {
    width: 80%;
    padding: 12px;
    font-size: 1.1rem;
    border-radius: 8px;
    background-color: #2196f3;
    color: #fff;
    border: none;
}

input#answerInput {
    width: 80%;
    max-width: 300px;
    padding: 10px;
    margin: 10px 0;
    font-size: 1.4rem;
    text-align: center;
    border: 2px solid #ccc;
    border-radius: 8px;
}

#answerInput::placeholder {
    font-size: 1rem;
    color: #999;
}

.toggle-audio {
    margin-bottom: 10px;
    text-align: center;
}

#audioBtn button {
    margin: 10px auto;
    background-color: #2196f3;
}

.message-container {
    font-size: 1.4rem;
    font-weight: bold;
    text-align: center;
    margin-top: 10px;
}

.message-container.success {
    color: #4caf50;
}

.message-container.error {
    color: #f44336;
}

.result-message {
    font-size: 1.4rem;
    margin-top: 12px;
    font-weight: bold;
    text-align: center;
}

.result-message.success {
    color: #4caf50;
}

.back-link {
    font-size: 1rem;
    text-align: center;
    margin-top: 20px;
}

.back-link a {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    justify-content: center;
    padding: 10px 20px;
    background: #4caf50;
    color: #fff;
    text-decoration: none;
    border-radius: 8px;
    font-weight: bold;
    transition: background 0.3s, transform 0.2s;
}

.back-link a:hover {
    background: #45a049;
    transform: translateY(-2px);
    text-decoration: none;
}

footer {
    text-align: center;
    font-size: 0.8rem;
    color: #555;
    font-weight: bold;
    margin-top: 20px;
}