body {
    font-family: Arial, sans-serif;
}
h1 {
    color: #333;
}
.course-container {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
}
.course-button {
    display: flex;
    align-items: center;
    background: #f4f4f4;
    padding: 20px;
    border-radius: 10px;
    cursor: pointer;
    border: 1px solid #ccc;
    flex: 1 1 calc(33.333% - 40px);
    box-sizing: border-box;
    position: relative;
}
.course-button img {
    width: 40px;
    height: 40px;
    margin-right: 20px;
}
.submenu {
    display: none;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 10px;
    position: absolute;
    left: 0;
    top: 100%;
    width: 100%;
    z-index: 1;
    background: #f4f4f4;
    border: 1px solid #ccc;
    border-radius: 10px;
    padding: 10px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    transition: opacity 0.3s ease, visibility 0.3s ease;
    opacity: 0;
    visibility: hidden;
}
.submenu.show {
    opacity: 1;
    visibility: visible;
}
.submenu-button {
    display: flex;
    align-items: center;
    background: #e9e9e9;
    padding: 10px;
    border-radius: 5px;
    cursor: pointer;
    border: 1px solid #bbb;
    flex: 1 1 calc(33.333% - 20px);
    box-sizing: border-box;
}
.submenu-button img {
    width: 20px;
    height: 20px;
    margin-right: 10px;
}
@media (max-width: 768px) {
    .course-button {
        flex: 1 1 calc(50% - 40px);
    }
    .submenu {
        position: static;
        margin-top: 10px;
        box-shadow: none;
        border: none;
        background: none;
        padding: 0;
    }
    .submenu-button {
        background: #f4f4f4;
        border: 1px solid #ccc;
        margin-top: 10px;
    }
}
@media (max-width: 480px) {
    .course-button, .submenu-button {
        flex: 1 1 100%;
    }
    .submenu {
        position: static;
        margin-top: 10px;
        box-shadow: none;
        border: none;
        background: none;
        padding: 0;
    }
    .submenu-button {
        background: #f4f4f4;
        border: 1px solid #ccc;
        margin-top: 10px;
    }
}