/* AI System Engineer Study Notes — Dark Glassmorphism Theme */

:root {
  --bg-primary: #0a0a1a;
  --bg-secondary: #111128;
  --glass: rgba(255, 255, 255, 0.05);
  --glass-border: rgba(255, 255, 255, 0.1);
  --glass-hover: rgba(255, 255, 255, 0.08);
  --neon-blue: #00d4ff;
  --neon-purple: #a855f7;
  --neon-green: #22c55e;
  --neon-yellow: #eab308;
  --neon-red: #ef4444;
  --neon-orange: #f97316;
  --text-primary: #e2e8f0;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --font-sans: 'Inter', -apple-system, sans-serif;
}

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

body {
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-sans);
  line-height: 1.7;
  min-height: 100vh;
}

/* Animated background */
body::before {
  content: '';
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background:
    radial-gradient(ellipse at 20% 50%, rgba(0, 212, 255, 0.08) 0%, transparent 50%),
    radial-gradient(ellipse at 80% 20%, rgba(168, 85, 247, 0.08) 0%, transparent 50%),
    radial-gradient(ellipse at 50% 80%, rgba(34, 197, 94, 0.05) 0%, transparent 50%);
  z-index: -1;
  animation: bgShift 20s ease-in-out infinite alternate;
}

@keyframes bgShift {
  0% { opacity: 0.8; }
  50% { opacity: 1; }
  100% { opacity: 0.8; }
}

/* Container */
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

/* Header */
.header {
  text-align: center;
  margin-bottom: 3rem;
  padding: 2rem;
  background: var(--glass);
  border: 1px solid var(--glass-border);
  border-radius: 20px;
  backdrop-filter: blur(20px);
}

.header .day-badge {
  display: inline-block;
  background: linear-gradient(135deg, var(--neon-blue), var(--neon-purple));
  color: white;
  font-size: 0.85rem;
  font-weight: 700;
  padding: 0.4rem 1.2rem;
  border-radius: 20px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 1rem;
}

.header h1 {
  font-size: 2rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--neon-blue), var(--neon-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.5rem;
}

.header .subtitle {
  color: var(--text-secondary);
  font-size: 1.05rem;
}

.header .meta {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-top: 1.2rem;
  color: var(--text-muted);
  font-size: 0.85rem;
}

.header .meta span {
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

/* Hero image */
.hero-image {
  width: 100%;
  border-radius: 16px;
  overflow: hidden;
  margin-bottom: 2rem;
  border: 1px solid var(--glass-border);
  position: relative;
}

.hero-image img {
  width: 100%;
  height: 280px;
  object-fit: cover;
  display: block;
  filter: brightness(0.85) saturate(1.2);
  transition: filter 0.3s;
}

.hero-image:hover img {
  filter: brightness(0.95) saturate(1.3);
}

.hero-image::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 60%;
  background: linear-gradient(transparent, var(--bg-primary));
  pointer-events: none;
}

/* Progress bar */
.progress-wrap {
  margin: 2rem 0;
  background: var(--glass);
  border: 1px solid var(--glass-border);
  border-radius: 12px;
  padding: 1rem 1.5rem;
}

.progress-wrap .label {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
}

.progress-bar {
  height: 6px;
  background: rgba(255,255,255,0.1);
  border-radius: 3px;
  overflow: hidden;
}

.progress-bar .fill {
  height: 100%;
  background: linear-gradient(90deg, var(--neon-blue), var(--neon-purple));
  border-radius: 3px;
  transition: width 0.5s ease;
}

/* Sections */
.section {
  background: var(--glass);
  border: 1px solid var(--glass-border);
  border-radius: 16px;
  padding: 1.5rem 2rem;
  margin-bottom: 1.5rem;
  backdrop-filter: blur(10px);
  transition: border-color 0.3s;
}

.section:hover {
  border-color: rgba(0, 212, 255, 0.3);
}

.section h2 {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.section h2 .icon {
  font-size: 1.4rem;
}

.section h3 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--neon-blue);
  margin: 1.2rem 0 0.6rem;
}

.section p, .section li {
  color: var(--text-secondary);
  line-height: 1.8;
}

.section ul, .section ol {
  padding-left: 1.5rem;
}

.section li {
  margin-bottom: 0.4rem;
}

.section li::marker {
  color: var(--neon-purple);
}

/* Key concepts — highlight boxes */
.concept {
  background: rgba(0, 212, 255, 0.06);
  border-left: 3px solid var(--neon-blue);
  padding: 1rem 1.2rem;
  border-radius: 0 10px 10px 0;
  margin: 0.8rem 0;
}

.concept strong {
  color: var(--neon-blue);
}

/* Resource cards */
.resource {
  display: flex;
  gap: 1rem;
  padding: 1rem;
  background: var(--glass-hover);
  border: 1px solid var(--glass-border);
  border-radius: 12px;
  margin: 0.6rem 0;
  text-decoration: none;
  color: inherit;
  transition: all 0.3s;
}

.resource:hover {
  border-color: var(--neon-purple);
  background: rgba(168, 85, 247, 0.08);
}

.resource .r-icon {
  font-size: 1.6rem;
  flex-shrink: 0;
}

.resource .r-content h4 {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.2rem;
}

.resource .r-content p {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.resource .r-tag {
  display: inline-block;
  font-size: 0.7rem;
  background: rgba(168, 85, 247, 0.2);
  color: var(--neon-purple);
  padding: 0.15rem 0.5rem;
  border-radius: 6px;
  margin-top: 0.3rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* Exercise box */
.exercise {
  background: rgba(34, 197, 94, 0.06);
  border: 1px solid rgba(34, 197, 94, 0.2);
  border-radius: 12px;
  padding: 1.2rem 1.5rem;
  margin: 1rem 0;
}

.exercise h3 {
  color: var(--neon-green) !important;
  margin-top: 0 !important;
}

.exercise .steps {
  counter-reset: step;
  list-style: none;
  padding-left: 0;
}

.exercise .steps li {
  counter-increment: step;
  padding-left: 2rem;
  position: relative;
  margin-bottom: 0.6rem;
}

.exercise .steps li::before {
  content: counter(step);
  position: absolute;
  left: 0;
  width: 1.4rem;
  height: 1.4rem;
  background: rgba(34, 197, 94, 0.2);
  color: var(--neon-green);
  border-radius: 50%;
  font-size: 0.75rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Code blocks */
code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: rgba(168, 85, 247, 0.15);
  color: var(--neon-purple);
  padding: 0.15em 0.4em;
  border-radius: 4px;
}

pre {
  background: var(--bg-secondary);
  border: 1px solid var(--glass-border);
  border-radius: 10px;
  padding: 1.2rem;
  overflow-x: auto;
  margin: 0.8rem 0;
}

pre code {
  background: none;
  color: var(--text-primary);
  padding: 0;
}

/* Navigation */
.nav {
  display: flex;
  justify-content: space-between;
  margin-top: 2rem;
  gap: 1rem;
}

.nav a {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.8rem 1.5rem;
  background: var(--glass);
  border: 1px solid var(--glass-border);
  border-radius: 12px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.9rem;
  transition: all 0.3s;
}

.nav a:hover {
  border-color: var(--neon-blue);
  color: var(--neon-blue);
}

/* Footer */
.footer {
  text-align: center;
  padding: 2rem;
  color: var(--text-muted);
  font-size: 0.8rem;
}

/* Responsive */
@media (max-width: 640px) {
  .container { padding: 1rem; }
  .header h1 { font-size: 1.5rem; }
  .header .meta { flex-direction: column; gap: 0.5rem; }
  .section { padding: 1rem 1.2rem; }
  .resource { flex-direction: column; gap: 0.5rem; }
}

/* Difficulty indicator */
.difficulty {
  display: inline-flex;
  gap: 3px;
  margin-left: 0.5rem;
}

.difficulty .dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--glass-border);
}

.difficulty .dot.active { background: var(--neon-yellow); }
.difficulty .dot.active.hard { background: var(--neon-red); }

/* Tags */
.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.8rem;
}

.tag {
  font-size: 0.75rem;
  padding: 0.2rem 0.6rem;
  border-radius: 6px;
  border: 1px solid var(--glass-border);
  color: var(--text-muted);
}

.tag.core { border-color: var(--neon-blue); color: var(--neon-blue); }
.tag.practice { border-color: var(--neon-green); color: var(--neon-green); }
.tag.theory { border-color: var(--neon-purple); color: var(--neon-purple); }
.tag.project { border-color: var(--neon-orange); color: var(--neon-orange); }