/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header Styles */
.header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 20px 0;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.header h1 {
    font-size: 2.5em;
    margin-bottom: 5px;
}

.header .tagline {
    font-size: 1.1em;
    opacity: 0.9;
}

/* Primary Navigation */
.primary-nav {
    background-color: #2c3e50;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.primary-nav ul {
    list-style: none;
    display: flex;
    flex-wrap: wrap;
}

.primary-nav li {
    margin: 0;
}

.primary-nav a {
    display: block;
    color: white;
    text-decoration: none;
    padding: 15px 20px;
    transition: background-color 0.3s;
}

.primary-nav a:hover,
.primary-nav a.active {
    background-color: #34495e;
}

/* Main Container */
.main-container {
    display: flex;
    min-height: calc(100vh - 250px);
}

/* Sidebar Styles */
.sidebar {
    width: 280px;
    background-color: #f8f9fa;
    border-right: 1px solid #dee2e6;
    padding: 20px;
    overflow-y: auto;
}

.sidebar h2 {
    color: #667eea;
    margin-bottom: 15px;
    font-size: 1.5em;
    padding-bottom: 10px;
    border-bottom: 2px solid #667eea;
}

.lesson-list {
    list-style: none;
}

.lesson-list li {
    margin-bottom: 5px;
}

.lesson-list a {
    display: block;
    color: #333;
    text-decoration: none;
    padding: 10px 15px;
    border-radius: 5px;
    transition: all 0.3s;
    border-left: 3px solid transparent;
}

.lesson-list a:hover {
    background-color: #e9ecef;
    border-left-color: #667eea;
    padding-left: 20px;
}

/* Content Area */
.content {
    flex: 1;
    padding: 0;
    background-color: white;
}

.content iframe {
    width: 100%;
    height: 100%;
    border: none;
    min-height: calc(100vh - 250px);
}

/* Footer */
.footer {
    background-color: #2c3e50;
    color: white;
    text-align: center;
    padding: 20px 0;
    margin-top: auto;
}

/* Responsive Design */
@media (max-width: 768px) {
    .main-container {
        flex-direction: column;
    }

    .sidebar {
        width: 100%;
        border-right: none;
        border-bottom: 1px solid #dee2e6;
    }

    .primary-nav ul {
        flex-direction: column;
    }

    .header h1 {
        font-size: 2em;
    }
}