:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #e74c3c;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    background-color: #f8f9fa;
}

.navbar-brand {
    font-weight: bold;
}

.hero-section {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 80px 0;
    text-align: center;
}

.card {
    border: none;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s ease;
    margin-bottom: 20px;
}

.card:hover {
    transform: translateY(-5px);
}

.card-header {
    background-color: var(--primary-color);
    color: black;
    font-weight: bold;
}

.code-block {
    background-color: #2d3748;
    color: #e2e8f0;
    padding: 15px;
    border-radius: 5px;
    font-family: 'Courier New', monospace;
    overflow-x: auto;
}

.command-example {
    background-color: #edf2f7;
    border-left: 4px solid var(--secondary-color);
    padding: 10px 15px;
    margin: 10px 0;
}

.alert-custom {
    border-left: 4px solid var(--accent-color);
}

.progress-container {
    background-color: #e9ecef;
    border-radius: 10px;
    margin: 20px 0;
}

.progress-bar {
    background-color: var(--secondary-color);
}

.topic-nav {
    position: sticky;
    top: 20px;
}

.topic-nav .nav-link {
    color: var(--primary-color);
    border-left: 3px solid transparent;
    padding: 8px 15px;
}

.topic-nav .nav-link.active {
    border-left-color: var(--accent-color);
    background-color: #e9ecef;
}

.practical-exercise {
    background-color: #fff3cd;
    border: 1px solid #ffeaa7;
    border-radius: 5px;
    padding: 15px;
    margin: 15px 0;
}