/* ============================================
   NEXUS.SG — Dark Tech Blog Design System
   ============================================ */

/* ── Tokens ── */
:root {
  --bg-deep: #050508;
  --bg-primary: #0a0a12;
  --bg-secondary: #10101a;
  --bg-card: #141420;
  --bg-card-hover: #1a1a2a;
  --bg-code: #0c0c16;

  --border-default: #1e1e30;
  --border-light: #2a2a40;
  --border-glow: rgba(0, 200, 255, 0.25);

  --accent-primary: #00c8ff;
  --accent-secondary: #7c3aed;
  --accent-tertiary: #06d6a0;
  --gradient-accent: linear-gradient(135deg, #00c8ff, #7c3aed);

  --text-heading: #f0f0f8;
  --text-primary: #c8c8d8;
  --text-secondary: #8080a0;
  --text-muted: #505068;
  --text-accent: #00c8ff;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  --font-mono: ui-monospace, 'Cascadia Code', 'Fira Code', Consolas, monospace;

  --max-width: 1100px;
  --content-width: 760px;
  --nav-height: 60px;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  --transition-fast: 0.15s ease;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.4);
  --glow-cyan: 0 0 30px rgba(0, 200, 255, 0.12);
}

/* ── Reset ── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.75;
  min-height: 100vh;
  overflow-x: hidden;
  background-image: radial-gradient(circle at 1px 1px, rgba(0,200,255,0.035) 1px, transparent 0);
  background-size: 32px 32px;
}
a { color: var(--text-accent); text-decoration: none; transition: color var(--transition-fast); }
a:hover { color: #7c3aed; }
img, svg { display: block; max-width: 100%; }
ul, ol { list-style: none; }
h1, h2, h3, h4 { color: var(--text-heading); font-weight: 600; line-height: 1.3; }
h1 { font-size: clamp(1.75rem, 4vw, 2.6rem); }
h2 { font-size: clamp(1.35rem, 3vw, 1.85rem); }
h3 { font-size: clamp(1.1rem, 2.5vw, 1.4rem); }
p { margin-bottom: 1rem; }

/* ── Layout ── */
.container { width: 100%; max-width: var(--max-width); margin: 0 auto; padding: 0 1.5rem; }
.content-narrow { max-width: var(--content-width); margin: 0 auto; }

/* ── Navigation ── */
.site-nav {
  position: sticky; top: 0; z-index: 100;
  height: var(--nav-height);
  background: rgba(10, 10, 18, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-default);
}
.nav-inner {
  display: flex; align-items: center; justify-content: space-between;
  height: 100%;
}
.nav-logo {
  display: flex; align-items: center; gap: 0.6rem;
  font-weight: 700; font-size: 1.15rem; color: var(--text-heading);
  letter-spacing: -0.02em;
}
.nav-logo:hover { color: var(--text-heading); }
.logo-dot { color: var(--accent-primary); }
.nav-links {
  display: flex; align-items: center; gap: 2rem;
}
.nav-links a {
  color: var(--text-secondary); font-size: 0.9rem; font-weight: 500;
  position: relative; padding: 0.25rem 0;
}
.nav-links a::after {
  content: ''; position: absolute; bottom: -2px; left: 0;
  width: 0; height: 2px; background: var(--gradient-accent);
  transition: width var(--transition);
}
.nav-links a:hover { color: var(--text-heading); }
.nav-links a:hover::after { width: 100%; }

/* hamburger */
.nav-toggle {
  display: none; flex-direction: column; gap: 5px;
  background: none; border: none; cursor: pointer; padding: 4px;
}
.nav-toggle span {
  display: block; width: 22px; height: 2px; background: var(--text-primary);
  transition: var(--transition); transform-origin: center;
}
.nav-toggle.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.nav-toggle.active span:nth-child(2) { opacity: 0; }
.nav-toggle.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* ── Hero ── */
.hero {
  position: relative; padding: 5rem 0 4rem;
  overflow: hidden;
}
.hero::before, .hero::after {
  content: ''; position: absolute; border-radius: 50%;
  pointer-events: none;
}
.hero::before {
  width: 500px; height: 500px;
  background: radial-gradient(circle, rgba(0,200,255,0.08), transparent 70%);
  top: -150px; right: -120px;
  animation: floatOrb 10s ease-in-out infinite;
}
.hero::after {
  width: 400px; height: 400px;
  background: radial-gradient(circle, rgba(124,58,237,0.07), transparent 70%);
  bottom: -100px; left: -80px;
  animation: floatOrb 12s ease-in-out infinite reverse;
}
@keyframes floatOrb {
  0%, 100% { transform: translate(0, 0); }
  50% { transform: translate(30px, -20px); }
}
.hero-content { position: relative; z-index: 1; }
.hero-greeting {
  font-size: 0.95rem; color: var(--accent-primary);
  font-weight: 500; margin-bottom: 0.75rem;
  display: flex; align-items: center; gap: 0.5rem;
}
.hero-greeting::before {
  content: ''; width: 24px; height: 2px; background: var(--accent-primary);
}
.hero h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  margin-bottom: 1rem; letter-spacing: -0.03em;
}
.hero h1 .gradient-text {
  background: var(--gradient-accent);
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-subtitle {
  font-size: 1.1rem; color: var(--text-secondary);
  max-width: 520px; line-height: 1.8;
}
.hero-line {
  margin-top: 2.5rem; height: 1px; max-width: 280px;
  background: linear-gradient(90deg, var(--accent-primary), transparent);
}

/* ── Section Header ── */
.section { padding: 3.5rem 0; }
.section-header {
  display: flex; align-items: center; gap: 0.75rem;
  margin-bottom: 2rem;
}
.section-header::before {
  content: ''; width: 4px; height: 1.4em;
  background: var(--gradient-accent); border-radius: 2px;
}

/* ── Article Cards Grid ── */
.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
}
.article-card {
  background: var(--bg-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  transition: var(--transition);
  position: relative; overflow: hidden;
  display: flex; flex-direction: column;
}
.article-card::before {
  content: ''; position: absolute;
  top: 0; left: 0; right: 0; height: 3px;
  background: var(--gradient-accent);
  transform: scaleX(0); transition: var(--transition);
  transform-origin: left;
}
.article-card:hover {
  border-color: var(--border-glow);
  transform: translateY(-4px);
  box-shadow: var(--glow-cyan);
  background: var(--bg-card-hover);
}
.article-card:hover::before { transform: scaleX(1); }

.card-category {
  display: inline-block; font-size: 0.7rem; font-weight: 600;
  text-transform: uppercase; letter-spacing: 0.08em;
  color: var(--accent-primary);
  background: rgba(0, 200, 255, 0.08);
  padding: 0.2rem 0.6rem; border-radius: 4px;
  margin-bottom: 0.85rem; width: fit-content;
}
.card-category.purple { color: var(--accent-secondary); background: rgba(124,58,237,0.1); }
.card-category.green { color: var(--accent-tertiary); background: rgba(6,214,160,0.1); }

.card-title {
  font-size: 1.15rem; font-weight: 600; margin-bottom: 0.65rem;
  line-height: 1.4;
}
.card-title a {
  color: var(--text-heading); transition: color var(--transition-fast);
}
.card-title a:hover { color: var(--accent-primary); }
/* make entire card clickable */
.card-title a::after {
  content: ''; position: absolute; inset: 0;
}
.card-excerpt {
  font-size: 0.88rem; color: var(--text-secondary);
  line-height: 1.7; flex: 1;
}
.card-meta {
  display: flex; align-items: center; gap: 0.5rem;
  font-size: 0.78rem; color: var(--text-muted);
  margin-top: 1.2rem; padding-top: 1rem;
  border-top: 1px solid var(--border-default);
}
.card-meta .sep { opacity: 0.4; }

/* ── Tags ── */
.tag {
  display: inline-block; font-size: 0.72rem; font-weight: 500;
  color: var(--text-secondary); border: 1px solid var(--border-default);
  padding: 0.15rem 0.55rem; border-radius: 4px;
  transition: var(--transition-fast);
}
.tag:hover { border-color: var(--accent-primary); color: var(--text-accent); }

/* ── Article Page ── */
.article-page { padding: 2rem 0 4rem; }
.back-link {
  display: inline-flex; align-items: center; gap: 0.35rem;
  font-size: 0.85rem; color: var(--text-secondary);
  margin-bottom: 2rem; font-weight: 500;
}
.back-link:hover { color: var(--text-accent); }

.article-header { margin-bottom: 2.5rem; }
.article-tags { display: flex; gap: 0.5rem; margin-bottom: 1rem; }
.article-header h1 {
  margin-bottom: 1rem;
  font-size: clamp(1.8rem, 4.5vw, 2.8rem);
  letter-spacing: -0.02em;
}
.article-meta {
  display: flex; align-items: center; gap: 0.6rem;
  font-size: 0.85rem; color: var(--text-muted);
}
.article-meta .sep { opacity: 0.4; }

/* article prose */
.article-body { color: var(--text-primary); }
.article-body h2 {
  margin-top: 2.5rem; margin-bottom: 1rem; padding-top: 1rem;
  border-top: 1px solid var(--border-default);
}
.article-body h3 { margin-top: 2rem; margin-bottom: 0.75rem; }
.article-body p { margin-bottom: 1.15rem; }
.article-body ul, .article-body ol {
  margin: 1rem 0; padding-left: 1.5rem;
}
.article-body ul { list-style: disc; }
.article-body ol { list-style: decimal; }
.article-body li { margin-bottom: 0.4rem; color: var(--text-primary); }
.article-body strong { color: var(--text-heading); font-weight: 600; }
.article-body a { text-decoration: underline; text-underline-offset: 2px; }
.article-body blockquote {
  margin: 1.5rem 0; padding: 1rem 1.25rem;
  border-left: 3px solid var(--accent-primary);
  background: rgba(0, 200, 255, 0.04);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--text-secondary); font-style: italic;
}
.article-body code {
  font-family: var(--font-mono); font-size: 0.85em;
  background: var(--bg-code); color: var(--accent-primary);
  padding: 0.15em 0.4em; border-radius: 4px;
}
.article-body pre {
  margin: 1.5rem 0; padding: 1.25rem 1.5rem;
  background: var(--bg-code); border: 1px solid var(--border-default);
  border-radius: var(--radius-md); overflow-x: auto;
  line-height: 1.6;
}
.article-body pre code {
  background: none; padding: 0; font-size: 0.82rem;
  color: var(--text-primary);
}

/* ── About Page ── */
.about-page { padding: 3rem 0 4rem; }
.about-header {
  text-align: center; margin-bottom: 3rem;
}
.about-avatar {
  width: 100px; height: 100px; border-radius: 50%;
  background: var(--gradient-accent);
  margin: 0 auto 1.5rem; display: flex;
  align-items: center; justify-content: center;
  box-shadow: 0 0 40px rgba(0, 200, 255, 0.15);
}
.about-avatar svg { opacity: 0.9; }
.about-bio {
  max-width: 560px; margin: 0 auto;
  color: var(--text-secondary); font-size: 1.05rem;
  text-align: center;
}

.about-section { margin-bottom: 3rem; }
.about-section h2 {
  margin-bottom: 1.5rem; display: flex;
  align-items: center; gap: 0.6rem;
}
.about-section h2::before {
  content: ''; width: 3px; height: 1.2em;
  background: var(--gradient-accent); border-radius: 2px;
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 1rem;
}
.skill-item {
  background: var(--bg-card); border: 1px solid var(--border-default);
  border-radius: var(--radius-md); padding: 1.25rem;
  transition: var(--transition);
}
.skill-item:hover {
  border-color: var(--border-glow);
  box-shadow: var(--glow-cyan);
}
.skill-name {
  font-weight: 600; font-size: 0.9rem; color: var(--text-heading);
  margin-bottom: 0.35rem;
}
.skill-desc {
  font-size: 0.8rem; color: var(--text-secondary); margin: 0;
}

.timeline { position: relative; padding-left: 1.75rem; }
.timeline::before {
  content: ''; position: absolute; left: 0; top: 0.5rem; bottom: 0.5rem;
  width: 2px; background: var(--border-default);
}
.timeline-item { position: relative; margin-bottom: 2rem; }
.timeline-item::before {
  content: ''; position: absolute; left: -1.75rem;
  top: 0.45rem; width: 10px; height: 10px;
  border-radius: 50%; background: var(--accent-primary);
  border: 2px solid var(--bg-primary);
  box-shadow: 0 0 8px rgba(0, 200, 255, 0.3);
}
.timeline-year {
  font-size: 0.78rem; font-weight: 600;
  color: var(--accent-primary); margin-bottom: 0.25rem;
}
.timeline-title {
  font-weight: 600; color: var(--text-heading);
  font-size: 0.95rem; margin-bottom: 0.2rem;
}
.timeline-desc { font-size: 0.85rem; color: var(--text-secondary); margin: 0; }

/* ── Social Links ── */
.social-links { display: flex; gap: 1rem; }
.social-link {
  display: flex; align-items: center; justify-content: center;
  width: 40px; height: 40px; border-radius: var(--radius-sm);
  background: var(--bg-card); border: 1px solid var(--border-default);
  color: var(--text-secondary); transition: var(--transition);
}
.social-link:hover {
  border-color: var(--accent-primary); color: var(--accent-primary);
  box-shadow: var(--glow-cyan);
}
.social-link svg { width: 18px; height: 18px; fill: currentColor; }

/* ── Footer ── */
.site-footer {
  border-top: 1px solid var(--border-default);
  padding: 2.5rem 0;
}
.footer-inner {
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: 1rem;
}
.footer-copy {
  font-size: 0.8rem; color: var(--text-muted);
}
.footer-links { display: flex; gap: 1.5rem; }
.footer-links a {
  font-size: 0.8rem; color: var(--text-muted);
}
.footer-links a:hover { color: var(--text-accent); }

/* ── Scroll Animation ── */
.fade-in {
  opacity: 0; transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-in.visible {
  opacity: 1; transform: translateY(0);
}

/* ── Gradient Text Utility ── */
.gradient-text {
  background: var(--gradient-accent);
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* ── Responsive ── */
@media (max-width: 768px) {
  .nav-toggle { display: flex; }
  .nav-links {
    position: fixed; top: var(--nav-height); left: 0; right: 0;
    background: rgba(10, 10, 18, 0.95);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-default);
    padding: 1.25rem 1.5rem;
    flex-direction: column; gap: 0.75rem;
    transform: translateY(-120%); opacity: 0;
    transition: var(--transition); pointer-events: none;
  }
  .nav-links.active {
    transform: translateY(0); opacity: 1; pointer-events: all;
  }
  .hero { padding: 3rem 0 2.5rem; }
  .articles-grid { grid-template-columns: 1fr; }
  .footer-inner { flex-direction: column; text-align: center; }
  .skills-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 480px) {
  .container { padding: 0 1rem; }
  .skills-grid { grid-template-columns: 1fr; }
  .article-card { padding: 1.25rem; }
}

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg-deep); }
::-webkit-scrollbar-thumb {
  background: var(--border-light); border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }