/* =============================================================
   Design System — Portfolio · Sian Siong (Edmond) Ng
   Accent: Electric Blue #3B82F6
   Display: Space Grotesk  |  Body: Inter  |  Mono: JetBrains Mono
   ============================================================= */

/* ── Google Fonts ─────────────────────────────────────────── */
@import url('https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;500;600;700&family=Inter:wght@400;500;600&family=JetBrains+Mono:wght@400;500&display=swap');

/* ── Design Tokens (dark default) ────────────────────────── */
:root {
  /* Backgrounds — slightly violet-tinged near-black for depth */
  --bg:        #0A0A0F;
  --bg-elev:   #111118;
  --bg-elev2:  #18181F;

  /* Text */
  --text:      #F0F0F5;
  --text-dim:  #6B6B80;
  --text-mute: #3A3A50;

  /* Accent */
  --accent:        #3B82F6;
  --accent-dim:    rgba(59, 130, 246, 0.15);
  --accent-glow:   rgba(59, 130, 246, 0.25);

  /* Borders */
  --border:    #1E1E2A;
  --border-hi: #2A2A3A;

  /* Typography */
  --font-sans:  'Inter', system-ui, sans-serif;
  --font-display: 'Space Grotesk', system-ui, sans-serif;
  --font-mono:  'JetBrains Mono', 'Fira Code', monospace;

  /* Layout */
  --maxw:       1120px;
  --topbar-h:   64px;

  /* Radius */
  --radius-sm:  6px;
  --radius-md:  10px;
  --radius-lg:  16px;

  /* Transitions */
  --ease:       cubic-bezier(0.4, 0, 0.2, 1);
  --dur:        200ms;
}

/* Light theme overrides */
:root[data-theme="light"] {
  --bg:        #F8F8FC;
  --bg-elev:   #FFFFFF;
  --bg-elev2:  #F0F0F6;
  --text:      #0F0F1A;
  --text-dim:  #5A5A70;
  --text-mute: #C0C0D0;
  --border:    #E0E0EC;
  --border-hi: #D0D0E0;
  --accent-dim: rgba(59, 130, 246, 0.10);
  --accent-glow: rgba(59, 130, 246, 0.15);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color var(--dur) var(--ease),
              color var(--dur) var(--ease);
}

img, svg { display: block; max-width: 100%; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

ul { list-style: none; }

/* ── Layout Container ─────────────────────────────────────── */
.container {
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 2rem);
}

/* ── Section base ─────────────────────────────────────────── */
.section {
  padding-block: clamp(6rem, 12vw, 10rem);
  /* Offset for sticky topbar so anchor nav doesn't hide headings */
  scroll-margin-top: var(--topbar-h);
}

.section-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--accent);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

.section-heading {
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 700;
  color: var(--text);
  margin-bottom: clamp(2rem, 5vw, 3.5rem);
  letter-spacing: -0.02em;
}

/* ── Topbar ───────────────────────────────────────────────── */
.topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--topbar-h);
  background-color: rgba(10, 10, 15, 0.82);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  transition: background-color var(--dur) var(--ease),
              border-color var(--dur) var(--ease);
}

:root[data-theme="light"] .topbar {
  background-color: rgba(248, 248, 252, 0.85);
}

.topbar-inner {
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 2rem);
  height: 100%;
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

/* Logo / brand */
.topbar-logo {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--accent);
  white-space: nowrap;
  flex-shrink: 0;
}
.topbar-logo:hover { text-decoration: none; opacity: 0.8; }

/* Nav links */
.topbar-nav {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  margin-left: auto;
}

.topbar-nav a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-dim);
  padding: 0.4rem 0.6rem;
  border-radius: var(--radius-sm);
  transition: color var(--dur) var(--ease),
              background-color var(--dur) var(--ease);
}
.topbar-nav a:hover {
  color: var(--text);
  background-color: var(--bg-elev2);
  text-decoration: none;
}

/* Topbar actions */
.topbar-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-shrink: 0;
}

/* Icon/text buttons in topbar */
.topbar-btn {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-dim);
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.35rem 0.65rem;
  cursor: pointer;
  transition: color var(--dur) var(--ease),
              border-color var(--dur) var(--ease),
              background-color var(--dur) var(--ease);
  white-space: nowrap;
}
.topbar-btn:hover {
  color: var(--text);
  border-color: var(--border-hi);
  background-color: var(--bg-elev2);
}

/* Resume download link styled as an accent button */
.topbar-resume {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-dim);
  border: 1px solid var(--accent);
  border-radius: var(--radius-sm);
  padding: 0.35rem 0.75rem;
  cursor: pointer;
  transition: background-color var(--dur) var(--ease),
              color var(--dur) var(--ease);
  white-space: nowrap;
}
.topbar-resume:hover {
  background: var(--accent);
  color: #fff;
  text-decoration: none;
}

/* Hamburger button */
.topbar-hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 36px;
  height: 36px;
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  padding: 8px 7px;
}

.topbar-hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background-color: var(--text-dim);
  border-radius: 2px;
  transition: transform var(--dur) var(--ease),
              opacity var(--dur) var(--ease);
}

/* Mobile nav drawer */
.topbar-mobile-nav {
  display: none;
  position: fixed;
  top: var(--topbar-h);
  left: 0;
  right: 0;
  background-color: var(--bg-elev);
  border-bottom: 1px solid var(--border);
  padding: 1rem;
  z-index: 99;
  flex-direction: column;
  gap: 0.25rem;
}

.topbar-mobile-nav a {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-dim);
  padding: 0.6rem 0.75rem;
  border-radius: var(--radius-sm);
  transition: color var(--dur) var(--ease),
              background-color var(--dur) var(--ease);
}
.topbar-mobile-nav a:hover {
  color: var(--text);
  background-color: var(--bg-elev2);
  text-decoration: none;
}

.topbar-mobile-nav .topbar-resume {
  margin-top: 0.5rem;
  display: block;
  text-align: center;
}

/* ── Responsive: ≤768px hamburger ────────────────────────── */
@media (max-width: 768px) {
  .topbar-nav { display: none; }
  .topbar-hamburger { display: flex; }

  .topbar.open .topbar-mobile-nav {
    display: flex;
  }

  /* Hamburger → X animation */
  .topbar.open .topbar-hamburger span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
  }
  .topbar.open .topbar-hamburger span:nth-child(2) {
    opacity: 0;
  }
  .topbar.open .topbar-hamburger span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
  }
}

/* ── Main content offset for fixed topbar ────────────────── */
main {
  padding-top: var(--topbar-h);
}

/* ── CTA Buttons ──────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.65rem 1.4rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  border: none;
  transition: transform var(--dur) var(--ease),
              box-shadow var(--dur) var(--ease),
              background-color var(--dur) var(--ease),
              color var(--dur) var(--ease);
  text-decoration: none;
}

.btn:hover { text-decoration: none; }

.btn-primary {
  background-color: var(--accent);
  color: #fff;
}
.btn-primary:hover {
  background-color: #2563EB;
  transform: translateY(-2px);
  box-shadow: 0 8px 24px var(--accent-glow);
}

.btn-ghost {
  background-color: transparent;
  color: var(--text);
  border: 1px solid var(--border-hi);
}
.btn-ghost:hover {
  background-color: var(--bg-elev2);
  border-color: var(--text-dim);
  transform: translateY(-2px);
}

/* ── Hero Section ─────────────────────────────────────────── */
#hero {
  min-height: calc(100svh - var(--topbar-h));
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding-block: clamp(4rem, 10vw, 7rem);
  position: relative;
  overflow: hidden;
}

/* Subtle grid background pattern — signature detail */
#hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(var(--border) 1px, transparent 1px),
    linear-gradient(90deg, var(--border) 1px, transparent 1px);
  background-size: 48px 48px;
  opacity: 0.35;
  pointer-events: none;
}

/* Radial accent fade at center */
#hero::after {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 60% 50% at 50% 40%, var(--accent-dim) 0%, transparent 70%);
  pointer-events: none;
}

.hero-inner {
  position: relative;
  z-index: 1;
}

/* Terminal-style prompt prefix before tagline */
.hero-prompt {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--accent);
  margin-bottom: 0.75rem;
  letter-spacing: 0.04em;
}

.hero-line {
  display: inline-block;
}

.hero-name {
  font-family: var(--font-display);
  font-size: clamp(2.5rem, 7vw, 5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.05;
  color: var(--text);
  margin-bottom: 0.75rem;
}

.hero-role {
  font-family: var(--font-mono);
  font-size: clamp(0.95rem, 2.5vw, 1.15rem);
  color: var(--accent);
  font-weight: 500;
  margin-bottom: 1.25rem;
  letter-spacing: 0.01em;
}

.hero-positioning {
  font-family: var(--font-display);
  font-size: clamp(1.25rem, 2.5vw, 1.75rem);
  font-weight: 600;
  color: var(--text);
  max-width: 34ch;
  line-height: 1.4;
  margin-top: 1.5rem;
  margin-bottom: 1.75rem;
}

.hero-sub {
  color: var(--text-dim);
  max-width: 62ch;
  margin-top: 1rem;
  line-height: 1.65;
}

.hero-sub,
.case-stat {
  font-variant-numeric: tabular-nums;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-dim);
  background: var(--bg-elev);
  border: 1px solid var(--border-hi);
  border-radius: 999px;
  padding: 0.3rem 0.85rem;
  margin-bottom: 2rem;
}

.hero-badge-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: #22C55E;
  box-shadow: 0 0 6px #22C55E;
  flex-shrink: 0;
}

.hero-ctas {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

/* ── Case Study Layout (#work, #how) ─────────────────────── */
.case {
  border-top: 1px solid var(--border);
  padding-block: clamp(3rem, 6vw, 4.5rem);
}

.case-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--accent);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

.case-title {
  font-family: var(--font-display);
  font-size: clamp(1.35rem, 2.5vw, 1.9rem);
  margin-bottom: 2rem;
  max-width: 26ch;
}

.case-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: clamp(2rem, 4vw, 4rem);
  align-items: start;
}

@media (max-width: 860px) {
  .case-grid {
    grid-template-columns: 1fr;
  }
}

.case-beat {
  border-left: 2px solid var(--border-hi);
  padding-left: 1.25rem;
  margin-bottom: 1.5rem;
}

.case-beat h4 {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-dim);
  margin-bottom: 0.35rem;
}

.case-beat-outcome {
  border-left-color: var(--accent);
}

.case-stat {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--accent);
  margin-top: 0.75rem;
}

.case-diagram {
  min-height: 280px;
  position: sticky;
  top: calc(var(--topbar-h) + 2rem);
  --dg-node: var(--bg-elev2);
  --dg-stroke: var(--border-hi);
  --dg-flow: var(--accent);
  --dg-fail: #EF4444;
  --dg-ok: #22C55E;
  --dg-text: var(--text-dim);
}

.case-diagram svg {
  width: 100%;
  height: auto;
}

/* ── Principles Grid (#how) ───────────────────────────────── */
.principles {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
}

@media (max-width: 700px) {
  .principles {
    grid-template-columns: 1fr;
  }
}

.principle {
  background: var(--bg);
  padding: 2rem;
}

.principle-num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--accent);
}

.principle h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin: 0.5rem 0 0.5rem;
}

.principle p {
  color: var(--text-dim);
  font-size: 0.95rem;
}

/* ── Demo Showcase (#demos) — full-width alternating rows ── */
.demo-showcase {
  display: flex;
  flex-direction: column;
  gap: 5rem;
}

.demo-row {
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  gap: 3.5rem;
  align-items: center;
}

.demo-row:nth-child(even) .demo-media {
  order: 2;
}

@media (max-width: 900px) {
  .demo-row {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
  .demo-row:nth-child(even) .demo-media {
    order: 0;
  }
}

/* The animated preview is the hero of each row — whole window is a link */
.demo-media {
  display: block;
  height: 380px;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  overflow: hidden;
  transition: border-color 0.25s ease, box-shadow 0.25s ease;
}

.demo-media:hover {
  border-color: var(--accent);
  box-shadow: 0 0 48px var(--accent-glow);
}

@media (max-width: 900px) {
  .demo-media {
    height: 260px;
  }
}

.demo-media svg {
  width: 100%;
  height: 100%;
  display: block;
}

.demo-info {
  position: relative;
}

.demo-num {
  font-family: var(--font-mono);
  font-size: 3rem;
  font-weight: 700;
  color: var(--accent);
  opacity: 0.18;
  display: block;
  line-height: 1;
  margin-bottom: 0.5rem;
}

.demo-info h3 {
  font-family: var(--font-display);
  font-size: 1.6rem;
  margin: 0 0 0.75rem;
}

.demo-info p {
  color: var(--text-dim);
  font-size: 1rem;
  line-height: 1.7;
}

.demo-stack {
  list-style: none;
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  padding: 0;
  margin: 1rem 0 0;
}

.demo-stack li {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--accent);
  background: var(--accent-dim);
  border: 1px solid var(--border);
  padding: 0.2rem 0.6rem;
}

.demo-links {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-top: 1.5rem;
}

/* SVG scene styling inside the preview */
.demo-media .dp-node rect {
  fill: var(--bg-elev2);
  stroke: var(--border);
  stroke-width: 1;
}

.demo-media text {
  font-family: var(--font-mono);
  font-size: 14px;
  fill: var(--text-dim);
}

.demo-media .dp-node-sm text {
  font-size: 12px;
}

.demo-media .dp-label {
  font-size: 12px;
  letter-spacing: 0.08em;
}

.demo-media .dp-wire {
  stroke: var(--border);
  stroke-width: 1;
}

.demo-media .dp-dot {
  fill: var(--accent);
}

.demo-media .dp-bubble-user rect {
  fill: var(--accent-dim);
  stroke: var(--accent);
  stroke-width: 1;
}

.demo-media .dp-bubble-user text {
  fill: var(--accent);
}

.demo-media .dp-bubble-bot rect,
.demo-media .dp-bubble-bot-bg {
  fill: var(--bg-elev2);
  stroke: var(--border);
  stroke-width: 1;
}

.demo-media .dp-tdot {
  fill: var(--text-dim);
}

.demo-media .dp-chrome {
  fill: var(--bg-elev2);
  stroke: var(--border);
  stroke-width: 1;
}

.demo-media .dp-chrome-title {
  font-size: 12px;
}

.demo-media .dp-term {
  font-size: 15px;
}

.demo-media .dp-term-cmd {
  fill: var(--text);
}

.demo-media .dp-term-ok,
.demo-media .dp-term-done {
  fill: #22C55E;
}

.demo-media .dp-cursor {
  fill: var(--accent);
}

/* ── Experience Section ──────────────────────────────────── */
#experience {
  background: var(--bg);
}

.xp-item {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 1.5rem;
  border-top: 1px solid var(--border);
  padding-block: 2rem;
}

@media (max-width: 700px) {
  .xp-item {
    grid-template-columns: 1fr;
    gap: 0.5rem;
  }
}

.xp-meta {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-dim);
}

.xp-title {
  font-family: var(--font-display);
  font-size: 1.1rem;
}

.xp-company {
  color: var(--accent);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
}

.xp-summary {
  color: var(--text-dim);
  max-width: 60ch;
}

/* ── Skills Section (tiered) ─────────────────────────────── */
#skills {
  background: var(--bg);
}

.tier {
  border-top: 1px solid var(--border);
  padding-block: 1.75rem;
}

.tier h3 {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text);
  margin-bottom: 0.6rem;
}

.tier-list {
  color: var(--text-dim);
  line-height: 1.9;
}

/* ── Contact Section ──────────────────────────────────────── */
#contact {
  background: var(--bg-elev);
  border-top: 1px solid var(--border);
  text-align: center;
}

.contact-inner {
  max-width: 560px;
  margin-inline: auto;
}

.contact-tagline {
  font-size: 1.05rem;
  color: var(--text-dim);
  margin-bottom: 2.5rem;
  line-height: 1.65;
}

.contact-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.75rem;
}

/* ── Footer ───────────────────────────────────────────────── */
footer {
  border-top: 1px solid var(--border);
  padding-block: 1.75rem;
  text-align: center;
}

.footer-copy {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-mute);
}

/* ── Focus visible for keyboard accessibility ─────────────── */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ── Reduced motion ───────────────────────────────────────── */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  html {
    scroll-behavior: auto;
  }
}