* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    padding: 20px;
}

.container-course {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.filters {
    display: flex;
    flex-direction: column;
    gap: 10px;
    align-items: center;
}

.subjects, .grades {
    text-align: center;
}

.buttons-row {
    display: flex;
    gap: 10px;
    justify-content: center;
    flex-wrap: wrap;
}

.subject-btn, .grade-btn {
    padding: 10px 20px;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

.subject-btn:hover, .grade-btn:hover {
    background-color: #0056b3;
}

.subject-btn.selected, .grade-btn.selected {
    background-color: #28a745;
}

.content-container {
    display: flex;
    gap: 20px;
}

.topics-list {
    width: 30%;
    background-color: #fff;
    padding: 10px;
    border-radius: 8px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.topics-list ul {
    list-style-type: none;
}

.topics-list ul li {
    padding: 5px;
    cursor: pointer;
    border-bottom: 1px solid #ddd;
}

.topics-list ul li:hover {
    background-color: #f0f0f0;
}

.content-area {
    width: 70%;
    background-color: #fff;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

#video-container iframe {
    width: 100%;
    height: 300px;
    margin-bottom: 20px;
}

.action-buttons {
    display: flex;
    gap: 10px;
}

.action-btn {
    padding: 10px 20px;
    background-color: #4CAF50; /* Yashil rang, o'zgartirish mumkin */
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

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