:root {
    --bg-base: #06060c;
    --bg-surface: rgba(255, 255, 255, 0.03);
    --bg-surface-hover: rgba(255, 255, 255, 0.08);
    --border-color: rgba(255, 255, 255, 0.08);
    --brand-primary: #7c3aed;
    --brand-light: #a78bfa;
    --brand-dark: #5b21b6;
    
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --diff-easy: #10b981;
    --diff-medium: #f59e0b;
    --diff-hard: #ef4444;
    
    --font-sans: 'Inter', sans-serif;
    --font-heading: 'Outfit', sans-serif;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-sans);
    background-color: var(--bg-base);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    position: relative;
}

html {
    scroll-behavior: smooth;
}

/* Background Effects */
.background-elements {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    overflow: hidden;
    pointer-events: none;
}

.glow-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(120px);
    opacity: 0.4;
}

.orb-1 {
    top: -20%;
    left: -10%;
    width: 60vw;
    height: 60vw;
    background: radial-gradient(circle, var(--brand-dark) 0%, transparent 70%);
}

.orb-2 {
    bottom: -30%;
    right: -10%;
    width: 70vw;
    height: 70vw;
    background: radial-gradient(circle, rgba(16, 185, 129, 0.05) 0%, transparent 70%);
}

.grid-overlay {
    position: absolute;
    inset: 0;
    background-image: 
        linear-gradient(rgba(255, 255, 255, 0.02) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255, 255, 255, 0.02) 1px, transparent 1px);
    background-size: 50px 50px;
    mask-image: radial-gradient(circle at center, black 40%, transparent 100%);
    -webkit-mask-image: radial-gradient(circle at center, black 40%, transparent 100%);
}

/* Typography & General Classes */
.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 2rem;
}

h1, h2, h3, h4, h5 {
    font-family: var(--font-heading);
    line-height: 1.2;
}

/* Top Navigation */
.top-nav {
    position: absolute;
    top: 2rem;
    left: 2rem;
    z-index: 100;
}

.return-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 500;
    transition: all 0.3s ease;
    padding: 0.5rem 1rem;
    border-radius: 9999px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-color);
    backdrop-filter: blur(10px);
}

.return-btn:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.08);
    border-color: rgba(255, 255, 255, 0.15);
    transform: translateX(-4px);
}

@media (max-width: 768px) {
    .top-nav {
        top: 1.5rem;
        left: 1.5rem;
    }
}

/* Header */
.header {
    padding: 4rem 0 3rem;
    text-align: center;
}

.logo-text {
    font-size: 2.5rem;
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 0.5rem;
    display: inline-flex;
    align-items: center;
    gap: 0.75rem;
}


.badge {
    font-size: 0.8rem;
    padding: 0.2rem 0.6rem;
    background: rgba(124, 58, 237, 0.2);
    color: var(--brand-light);
    border: 1px solid rgba(124, 58, 237, 0.4);
    border-radius: 9999px;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    transform: translateY(-5px);
}

.header .subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    max-width: 600px;
    margin: 0 auto;
}

/* Path Sections */
.path-section {
    margin-bottom: 2rem;
}

.path-header {
    background: linear-gradient(145deg, rgba(255,255,255,0.05) 0%, rgba(255,255,255,0.01) 100%);
    border: 1px solid var(--border-color);
    border-radius: 1.5rem;
    padding: 2.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    backdrop-filter: blur(10px);
    position: relative;
    overflow: hidden;
    cursor: pointer;
    transition: all 0.3s ease;
    z-index: 10;
}

.path-header:hover {
    border-color: rgba(124, 58, 237, 0.4);
    background: linear-gradient(145deg, rgba(255,255,255,0.08) 0%, rgba(255,255,255,0.02) 100%);
    transform: translateY(-2px);
    box-shadow: 0 10px 30px -10px rgba(124, 58, 237, 0.2);
}

.path-header::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: linear-gradient(90deg, transparent, var(--brand-primary), transparent);
    opacity: 0.5;
    transition: opacity 0.3s ease;
}

.path-header:hover::before {
    opacity: 1;
}

.path-header-content {
    text-align: left;
    max-width: 80%;
}

.path-header h2 {
    font-size: 2.2rem;
    margin-bottom: 0.75rem;
    background: linear-gradient(to right, #fff, var(--text-secondary));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.path-header p {
    color: var(--text-secondary);
    font-size: 1.05rem;
    margin-bottom: 1.5rem;
}

.path-stats {
    display: flex;
    justify-content: flex-start;
    gap: 1.5rem;
}

.path-stats span {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-muted);
    font-weight: 500;
    background: rgba(255,255,255,0.03);
    padding: 0.4rem 0.8rem;
    border-radius: 0.5rem;
    border: 1px solid rgba(255,255,255,0.05);
    font-size: 0.9rem;
}

.path-toggle-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(255,255,255,0.05);
    border-radius: 50%;
    color: var(--brand-primary);
    transition: transform 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.path-section.expanded .path-toggle-icon {
    transform: rotate(180deg);
    background: var(--brand-primary);
    color: #fff;
    box-shadow: 0 0 15px rgba(124, 58, 237, 0.5);
}

/* Accordion Content Layout */
.path-content {
    display: grid;
    grid-template-rows: 0fr;
    transition: grid-template-rows 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.path-content > div {
    overflow: hidden;
}

.path-section.expanded .path-content > div {
    overflow: visible;
}

.path-section.expanded .path-content {
    grid-template-rows: 1fr;
}

/* Timeline */
.timeline-container {
    position: relative;
    padding: 3rem 0 2rem 0;
}

.timeline-progress-bar {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 24px;
    transform: translateX(-50%);
    width: 4px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 2px;
}

.timeline-progress-fill {
    position: absolute;
    top: 0;
    bottom: 100%;
    left: 0;
    width: 100%;
    background: linear-gradient(to bottom, var(--brand-light), var(--brand-primary));
    border-radius: 2px;
    box-shadow: 0 0 15px var(--brand-primary);
    transition: bottom 0.1s ease;
}

/* Timeline Cards */
.timeline-item {
    display: flex;
    justify-content: flex-start;
    padding-left: 48px;
    position: relative;
    margin-bottom: 2rem;
    width: 100%;
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s cubic-bezier(0.2, 0.8, 0.2, 1), transform 0.6s cubic-bezier(0.2, 0.8, 0.2, 1);
}

.timeline-item.visible {
    opacity: 1;
    transform: translateY(0);
}

.timeline-dot {
    position: absolute;
    width: 24px;
    height: 24px;
    background-color: var(--bg-base);
    border: 4px solid var(--border-color);
    border-radius: 50%;
    left: 24px;
    top: 50%;
    transform: translate(-50%, -50%);
    z-index: 2;
    transition: all 0.3s ease;
}

.timeline-dot::after {
    content: '';
    position: absolute;
    inset: 2px;
    background-color: var(--brand-primary);
    border-radius: 50%;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.timeline-item.active .timeline-dot {
    border-color: var(--brand-primary);
    box-shadow: 0 0 0 4px rgba(124, 58, 237, 0.2);
}

.timeline-item.active .timeline-dot::after {
    opacity: 1;
}

.timeline-content {
    width: 100%;
    margin-left: 1rem;
    background: var(--bg-surface);
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    padding: 1.5rem;
    backdrop-filter: blur(10px);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    cursor: default;
    text-decoration: none;
    display: block;
    color: var(--text-primary);
}

a.timeline-content:hover {
    transform: translateY(-5px) scale(1.02);
    transform-origin: left center;
    border-color: var(--brand-primary);
    background: var(--bg-surface-hover);
    box-shadow: 0 10px 30px -10px rgba(124, 58, 237, 0.3);
}

.content-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
    gap: 1rem;
}

.course-type {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 600;
    color: var(--text-muted);
}

h3.course-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-top: 0.25rem;
    color: var(--text-primary);
    transition: color 0.3s ease;
}

a.timeline-content:hover h3.course-title {
    color: var(--brand-light);
}

.badge-difficulty {
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    background: rgba(255, 255, 255, 0.05);
}

.diff-easy { color: var(--diff-easy); background: rgba(16, 185, 129, 0.1); border: 1px solid rgba(16, 185, 129, 0.2); }
.diff-medium { color: var(--diff-medium); background: rgba(245, 158, 11, 0.1); border: 1px solid rgba(245, 158, 11, 0.2); }
.diff-hard { color: var(--diff-hard); background: rgba(239, 68, 68, 0.1); border: 1px solid rgba(239, 68, 68, 0.2); }

.content-footer {
    display: flex;
    justify-content: flex-end;
    margin-top: 1rem;
    border-top: 1px solid var(--border-color);
    padding-top: 1rem;
}

.action-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--brand-primary);
    transition: all 0.3s ease;
}

a.timeline-content:hover .action-link {
    color: var(--brand-light);
    transform: translateX(4px);
}

.missing-link {
    color: var(--text-muted);
    font-size: 0.875rem;
    font-style: italic;
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem 0;
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
}

/* Responsive */
@media (max-width: 768px) {
    .path-header {
        padding: 2rem;
    }
    
    .path-header h2 {
        font-size: 2rem;
    }
}