/* Base and Layout Styles */
body {
    font-family: 'Inter', 'Noto Sans JP', sans-serif;
    scroll-behavior: smooth;
    background-color: #f8f9fa; /* A slightly off-white background */
    color: #212529;
}

.gradient-bg {
    background: linear-gradient(135deg, #e9ecef 0%, #dee2e6 100%);
}

.card {
    background-color: white;
    border-radius: 12px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    border: 1px solid #e9ecef;
}

/* Header Navigation (from header.php) */
.nav-header-link {
    position: relative;
    padding: 0.5rem 0.25rem;
    color: #495057;
    text-decoration: none;
    transition: color 0.3s ease;
}

.nav-header-link::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    background-color: #007bff;
    transition: width 0.3s ease;
}

.nav-header-link:hover {
    color: #007bff;
}

.nav-header-link:hover::after {
    width: 100%;
}

/* Sidebar Navigation (for lecture pages) */
.sticky-nav {
    position: sticky;
    top: 6rem; /* Adjust based on header height */
    align-self: start;
}

.nav-link {
    transition: all 0.2s ease-in-out;
    border-left: 3px solid transparent;
    color: #495057;
}

.nav-link:hover {
    color: #007bff;
    border-left-color: #007bff;
    background-color: #e9ecef;
    transform: translateX(5px);
}

.nav-link.active {
    color: #007bff;
    border-left-color: #007bff;
    font-weight: 600;
}

/* Typography */
h2 {
    font-family: 'Noto Sans JP', sans-serif;
    font-weight: 700;
}

h3, h4, h5 {
    font-family: 'Noto Sans JP', sans-serif;
    font-weight: 500;
}

.prose p, .prose ul, .prose ol, .prose h4, .prose table, .prose pre { 
    margin-top: 1em; 
    margin-bottom: 1em; 
}
.prose ul {
    list-style-position: inside;
}
.prose ol {
    list-style-position: inside;
    list-style-type: decimal;
}
.prose ol ul, .prose ul ul {
    list-style-type: disc;
    padding-left: 2rem;
}

/* Component Styles */
.case-study {
    border-left: 4px solid #007bff;
    background-color: #f1f3f5;
    padding: 1rem;
    border-radius: 0.25rem;
}
.code-block {
    background-color: #2d3748;
    color: #e2e8f0;
    padding: 1rem;
    border-radius: 0.5rem;
    overflow-x: auto;
    font-family: 'Courier New', Courier, monospace;
    font-size: 0.875rem;
}
.timeline {
    position: relative;
    padding-left: 2rem;
    border-left: 2px solid #dee2e6;
}
.timeline-item {
    position: relative;
    padding-bottom: 1.5rem;
}
.timeline-item:last-child {
    padding-bottom: 0;
}
.timeline-dot {
    position: absolute;
    left: -2.5rem;
    top: 0.25rem;
    height: 1rem;
    width: 1rem;
    border-radius: 50%;
    background-color: #fff;
    border: 3px solid #007bff;
}
.matrix-cell { 
    padding: 0.75rem; 
    border-radius: 0.375rem; 
}
.matrix-low { 
    background-color: #d4edda; 
    color: #155724;
}
.matrix-medium { 
    background-color: #fff3cd; 
    color: #856404;
}
.matrix-high { 
    background-color: #f8d7da; 
    color: #721c24;
}
.flowchart-symbol {
    background-color: #e9ecef;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    border: 1px solid #ced4da;
    display: inline-block;
}