.lesson-block {
    max-width: 400px;
    margin: 20px auto;
    font-family: sans-serif;
    border: 1px solid #ccc;
    padding: 15px;
    border-radius: 8px;
    background-color: #f9f9f9;
}
.board-container {
    width: 100%;
    margin-bottom: 10px;
}
.controls {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-bottom: 15px;
}
.controls button {
    padding: 5px 15px;
    cursor: pointer;
    border: 1px solid #999;
    border-radius: 4px;
    background-color: #fff;
}
.controls button:hover { background-color: #eee; }
.lesson-text h3 { margin-top: 0; }