/* --- Custom Fonts Import --- */
@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:ital,wght@0,300..800;1,300..800&family=Syne:wght@700;800&family=JetBrains+Mono:wght@400;700&display=swap');

/* --- CSS Variables & Design Tokens --- */
:root {
  /* Dark Theme (Default) */
  --bg-color: oklch(0.12 0.005 250);
  --bg-lift: oklch(0.16 0.005 250);
  --text-primary: oklch(0.96 0.002 250);
  --text-secondary: oklch(0.75 0.005 250);
  --text-muted: oklch(0.50 0.005 250);
  --accent-color: oklch(0.78 0.08 245);
  --accent-rgb: 150, 175, 205;
  --border: oklch(0.22 0.005 250);
  --overlay-bg: rgba(10, 11, 12, 0.75);

  /* Fonts */
  --font-display: 'Syne', sans-serif;
  --font-body: 'Plus Jakarta Sans', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Spacing */
  --space-xs: clamp(0.5rem, 1vw, 0.75rem);
  --space-sm: clamp(0.75rem, 2vw, 1.25rem);
  --space-md: clamp(1.25rem, 3vw, 2rem);
  --space-lg: clamp(2rem, 5vw, 3.5rem);
  --space-xl: clamp(3.5rem, 8vw, 6rem);
  
  /* Transitions */
  --transition-smooth: all 0.35s cubic-bezier(0.25, 1, 0.5, 1);
  --transition-fast: all 0.15s ease-out;
}

[data-theme="light"] {
  /* Light Theme */
  --bg-color: oklch(0.98 0.002 250);
  --bg-lift: oklch(0.94 0.005 250);
  --text-primary: oklch(0.16 0.005 250);
  --text-secondary: oklch(0.42 0.005 250);
  --text-muted: oklch(0.62 0.005 250);
  --accent-color: oklch(0.48 0.10 245);
  --accent-rgb: 75, 105, 140;
  --border: oklch(0.88 0.002 250);
  --overlay-bg: rgba(240, 242, 245, 0.75);
}

/* --- Reset & Global --- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  background-color: var(--bg-color);
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding: var(--space-md) var(--space-md) 0 var(--space-md);
  max-width: 1400px;
  margin: 0 auto;
  position: relative;
  transition: background-color 0.4s ease, color 0.4s ease;
}

a {
  color: inherit;
  text-decoration: none;
  transition: var(--transition-fast);
}

button {
  background: none;
  border: none;
  color: inherit;
  font-family: inherit;
  cursor: pointer;
}

/* --- Focus States for Accessibility --- */
a:focus-visible, button:focus-visible {
  outline: 2px solid var(--accent-color);
  outline-offset: 4px;
}

/* --- Layout Elements --- */
header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  border-bottom: 1px solid var(--border);
  padding-bottom: var(--space-sm);
  margin-bottom: var(--space-lg);
}

.logo-group {
  display: flex;
  flex-direction: column;
}

.logo {
  font-family: var(--font-body);
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1;
}

.logo-subtitle {
  font-size: clamp(0.75rem, 1.5vw, 0.88rem);
  color: var(--text-secondary);
  font-family: var(--font-mono);
  margin-top: 4px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
}

nav {
  display: flex;
  gap: var(--space-md);
  align-items: center;
}

.nav-link {
  font-size: clamp(0.9rem, 1.5vw, 1.05rem);
  font-weight: 500;
  position: relative;
  padding: 4px 0;
  color: var(--text-secondary);
}

.nav-link:hover {
  color: var(--text-primary);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 1px;
  background-color: var(--accent-color);
  transition: var(--transition-smooth);
}

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

.theme-btn {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  border: 1px solid var(--border);
  transition: var(--transition-smooth);
}

.theme-btn:hover {
  background-color: var(--bg-lift);
  border-color: var(--accent-color);
  color: var(--accent-color);
  transform: rotate(15deg);
}

.theme-btn svg {
  width: 18px;
  height: 18px;
  fill: currentColor;
}

/* Hide theme icon variants */
[data-theme="light"] .sun-icon,
[data-theme="dark"] .moon-icon {
  display: none;
}

/* --- Homepage Layout --- */
.hero {
  max-width: 800px;
  margin-bottom: var(--space-xl);
}

.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5vw, 3.8rem);
  line-height: 1.1;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: var(--space-md);
}

.hero p {
  font-size: clamp(1.05rem, 2vw, 1.3rem);
  color: var(--text-secondary);
  max-width: 680px;
  line-height: 1.5;
  font-weight: 300;
}

/* Course Grid */
.course-grid-title {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--text-muted);
  margin-bottom: var(--space-sm);
  border-bottom: 1px solid var(--border);
  padding-bottom: var(--space-xs);
}

.courses-list {
  display: grid;
  grid-template-columns: 1fr;
  border-left: 1px solid var(--border);
  border-top: 1px solid var(--border);
  margin-bottom: var(--space-xl);
}

@media (min-width: 768px) {
  .courses-list {
    grid-template-columns: repeat(2, 1fr);
  }
}

.course-card {
  border-right: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  padding: var(--space-md);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  min-height: 240px;
  position: relative;
  overflow: hidden;
  transition: var(--transition-smooth);
}

.course-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--accent-color);
  opacity: 0;
  z-index: 0;
  transition: var(--transition-smooth);
}

.course-card:hover {
  transform: translateY(-4px);
  border-color: var(--accent-color);
}

.course-card:hover::before {
  opacity: 0.03;
}

.course-card-index {
  font-family: var(--font-mono);
  font-size: clamp(1rem, 2vw, 1.2rem);
  color: var(--accent-color);
  margin-bottom: var(--space-md);
  z-index: 1;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.course-card-index svg {
  width: 16px;
  height: 16px;
  opacity: 0;
  transform: translateX(-8px);
  transition: var(--transition-smooth);
}

.course-card:hover .course-card-index svg {
  opacity: 1;
  transform: translateX(0);
}

.course-card-content {
  z-index: 1;
}

.course-card-title {
  font-family: var(--font-display);
  font-size: clamp(1.4rem, 2.5vw, 1.8rem);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--space-xs);
  letter-spacing: -0.01em;
}

.course-card-inst {
  font-size: 0.9rem;
  color: var(--text-secondary);
  font-family: var(--font-body);
}

/* --- Course Detail Page Layout --- */
.course-detail {
  display: none;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
  margin-bottom: var(--space-xl);
  animation: fadeIn 0.4s ease-out;
}

@media (min-width: 992px) {
  .course-detail {
    grid-template-columns: 320px 1fr;
    gap: var(--space-xl);
  }
}

.course-sidebar {
  border-bottom: 1px solid var(--border);
  padding-bottom: var(--space-md);
}

@media (min-width: 992px) {
  .course-sidebar {
    border-bottom: none;
    border-right: 1px solid var(--border);
    padding-bottom: 0;
    padding-right: var(--space-md);
    position: sticky;
    top: var(--space-md);
    height: fit-content;
  }
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  text-transform: uppercase;
  color: var(--accent-color);
  margin-bottom: var(--space-md);
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: 4px;
  transition: var(--transition-smooth);
}

.back-link:hover {
  background-color: var(--bg-lift);
  border-color: var(--accent-color);
  transform: translateX(-4px);
}

.sidebar-meta {
  margin-top: var(--space-md);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.meta-item {
  display: flex;
  flex-direction: column;
}

.meta-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--text-muted);
  letter-spacing: 0.1em;
  margin-bottom: 4px;
}

.meta-value {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-primary);
}

.meta-value a {
  color: var(--accent-color);
  border-bottom: 1px solid transparent;
}

.meta-value a:hover {
  border-bottom-color: var(--accent-color);
}

/* Course Main Column */
.course-main-content {
  display: flex;
  flex-direction: column;
}

.course-main-header {
  border-bottom: 1px solid var(--border);
  padding-bottom: var(--space-md);
  margin-bottom: var(--space-md);
}

.course-header-inst {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  text-transform: uppercase;
  color: var(--accent-color);
  letter-spacing: 0.1em;
  margin-bottom: var(--space-xs);
}

.course-header-title {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: var(--space-sm);
}

.course-description {
  font-size: clamp(1rem, 1.8vw, 1.15rem);
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: var(--space-lg);
  font-weight: 300;
}

.section-title {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: var(--space-md);
  letter-spacing: -0.01em;
  display: flex;
  align-items: center;
  gap: 12px;
}

.section-title::after {
  content: '';
  flex-grow: 1;
  height: 1px;
  background-color: var(--border);
}

/* Course Schedule Items */
.schedule-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.schedule-item {
  border: 1px solid var(--border);
  background-color: var(--bg-lift);
  border-radius: 6px;
  padding: var(--space-md);
  transition: var(--transition-smooth);
}

.schedule-item:hover {
  border-color: var(--accent-color);
  box-shadow: 0 4px 20px rgba(var(--accent-rgb), 0.05);
}

.schedule-item-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 8px;
  border-bottom: 1px solid var(--border);
  padding-bottom: 8px;
  margin-bottom: var(--space-sm);
}

.schedule-item-title {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 700;
}

.schedule-item-date {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--accent-color);
}

.schedule-item-content {
  font-size: 0.95rem;
  color: var(--text-secondary);
}

.schedule-topics {
  margin-left: 1.25rem;
  margin-top: 6px;
  margin-bottom: 10px;
}

.schedule-topics li {
  margin-bottom: 4px;
}

.schedule-deliverable {
  font-size: 0.9rem;
  background-color: var(--bg-color);
  border-left: 3px solid var(--accent-color);
  padding: 6px 12px;
  border-radius: 0 4px 4px 0;
  margin-top: 10px;
}

.deliverable-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--accent-color);
  display: block;
  font-weight: 700;
}

/* Sidebar lists (Prerequisites) */
.sidebar-list {
  margin-left: 1.1rem;
  font-size: 0.9rem;
  color: var(--text-secondary);
  display: flex;
  flex-direction: column;
  gap: 4px;
}

/* --- Bio Drawer / Overlay --- */
.bio-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--overlay-bg);
  backdrop-filter: blur(4px);
  z-index: 100;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.4s ease;
}

.bio-overlay.active {
  opacity: 1;
  pointer-events: auto;
}

.bio-drawer {
  position: fixed;
  top: 0;
  right: -100%;
  width: 100%;
  max-width: 580px;
  height: 100%;
  background-color: var(--bg-lift);
  border-left: 1px solid var(--border);
  z-index: 101;
  padding: var(--space-lg);
  overflow-y: auto;
  box-shadow: -10px 0 30px rgba(0,0,0,0.15);
  transition: right 0.4s cubic-bezier(0.25, 1, 0.5, 1);
  display: flex;
  flex-direction: column;
}

.bio-drawer.active {
  right: 0;
}

.bio-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-md);
  border-bottom: 1px solid var(--border);
  padding-bottom: var(--space-sm);
}

.bio-title {
  font-family: var(--font-display);
  font-size: 1.8rem;
  font-weight: 800;
}

.close-btn {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border);
  border-radius: 50%;
  transition: var(--transition-smooth);
}

.close-btn:hover {
  background-color: var(--bg-color);
  border-color: var(--accent-color);
  color: var(--accent-color);
}

.close-btn svg {
  width: 16px;
  height: 16px;
}

.bio-body {
  flex-grow: 1;
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text-secondary);
}

.bio-body p {
  margin-bottom: var(--space-md);
  font-weight: 300;
}

.bio-body pstrong {
  font-weight: 600;
  color: var(--text-primary);
}

.bio-projects-title {
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-top: var(--space-md);
  margin-bottom: var(--space-sm);
}

.bio-projects {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.bio-project-item {
  border-bottom: 1px solid var(--border);
  padding-bottom: 8px;
}

.bio-project-name {
  font-weight: 600;
  color: var(--accent-color);
}

.bio-project-desc {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* --- Footer --- */
footer {
  border-top: 1px solid var(--border);
  padding: var(--space-md) 0;
  margin-top: auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-sm);
  font-size: 0.85rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

/* --- Animation Utilities --- */
.fade-out {
  opacity: 0;
  transition: opacity 0.15s ease-out;
}

.fade-in {
  opacity: 1;
  animation: fadeInEffect 0.35s cubic-bezier(0.25, 1, 0.5, 1) forwards;
}

@keyframes fadeInEffect {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Custom Scrollbar */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}
::-webkit-scrollbar-track {
  background: var(--bg-color);
}
::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--accent-color);
}