body {
    margin: 0;
    font-family: Arial, sans-serif;
    background: #f5f7fb;
    color: #222;
}
.course-header {
    padding: 20px;
}
.nav-container {
    display: flex;
    align-items: center;
}

#back-to-home {
    text-decoration: none;
    color: rgb(255, 255, 255);
    font-size: 15px;
    background-color: rgb(46, 78, 236);
    border-radius: 10px;
    padding: 10px;
}

.course-links {
    margin-left: auto;
    display: flex;
    gap: 10px;
}

.course-nav {
    text-decoration: none;
    background-color: rgb(73, 201, 244);
    color: rgb(0, 0, 0);
    font-size: 15px;
    border-radius: 10px;
    padding: 10px;
}
#thumnil-image{
    width: 980px;
    height: 520px;
    border-radius: 30px;
}


.course-body {
    display: flex;
    gap: 40px;
    max-width: 1400px;
    margin: 30px auto;
    padding: 0 20px;
        align-items: flex-start;

}

.toc-sidebar {
    width: 280px;
    background: #f5f5f5;
    padding: 20px;
    position: sticky;
    top: 20px;
    height: fit-content;
}

.toc-sidebar h3 {
    margin-top: 0;
    margin-bottom: 20px;
    font-size: 28px;
    font-weight: 600;
    color: #324a67;
}

.toc-sidebar ul {
    list-style: none;
    padding-left: 0;
    margin: 0;
}

.toc-sidebar > ul > li {
    margin-bottom: 18px;
}

.toc-sidebar a {
    text-decoration: none;
    color: #6b7f99;
    font-size: 16px;
    display: block;
    padding: 6px 0;
    transition: 0.3s;
}

.toc-sidebar a:hover {
    color: #2563eb;
}

.toc-sidebar ul ul {
    margin-top: 8px;
    margin-left: 20px;
}

.toc-sidebar ul ul a {
    font-size: 15px;
    color: #7a8ca5;
}

/* Main Content */
.course-content {
    flex: 1;
    background: white;
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 3px 12px rgba(0,0,0,0.1);
}

#thumbnail-image {
    width: 100%;
    border-radius: 12px;
    margin-bottom: 20px;
}

.course-content h2 {
    color: #0d6efd;
    margin-top: 40px;
}

.course-content h3 {
    color: #333;
}

.course-content p {
    line-height: 1.8;
}

.course-content ul li {
    margin-bottom: 10px;
}
.java-features {
    padding-left: 25px;
    margin: 20px 0;
}

.java-features li {
    margin-bottom: 20px;
    line-height: 1.9;
    font-size: 18px;
    color: #556b8d;
}

.java-features strong {
    color: #3b5b8c;
    font-weight: 700;
}

.java-table-wrapper {
    overflow-x: auto;
    margin: 25px 0;
}

.course-image {
    display: block;
    width: 80%;
    max-width: 800px;
    height: auto;
    margin: 30px auto;
    border-radius: 10px;
}

.java-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 18px;
    line-height: 1.8;
}

.java-table th {
    text-align: left;
    padding: 18px 15px;
    border-bottom: 1px solid #d9dee7;
    color: #1f2937;
    font-weight: 700;
}

.java-table td {
    padding: 18px 15px;
    border-bottom: 1px solid #e5e7eb;
    color: #222a37;
    vertical-align: top;
}

.java-table tbody tr:last-child td {
    border-bottom: none;
}

.java-table strong {
    color: #3b5b8c;
}

.java-table em {
    font-style: italic;
}

.code-container {
    position: relative;
    background: #00002c;
    border-radius: 12px;
    margin: 30px 0;
    overflow: hidden;
}

.code-container pre {
    margin: 0;
    padding: 25px;
    overflow-x: auto;
}

.code-container code {
    color: #e2e8f0;
    font-size: 16px;
    line-height: 1.8;
    font-family: "Fira Code", Consolas, monospace;
}

.copy-btn {
    position: absolute;
    top: 12px;
    right: 12px;
    width: 42px;
    height: 42px;
    border: 1px solid rgba(255,255,255,0.2);
    border-radius: 10px;
    background: transparent;
    color: white;
    cursor: pointer;
    font-size: 18px;
}

.copy-btn:hover {
    background: rgba(13, 36, 105, 0.838);
}

/* Mobile */
@media (max-width: 992px) {
    .course-body {
        flex-direction: column;
    }

    .toc-sidebar {
        width: 100%;
        position: relative;
        top: 0;
    }
    .course-image {
        width: 100%;
    }
}
@media (max-width: 768px) {
    .course-image {
        width: 100%;
    }
}