:root {
  --bg: #0a0c10;
  --fg: #e8eaed;
  --fg-dim: #9aa2ad;
  --accent: #6ee7f2;
  --accent-dim: #2b5b60;
  --card-bg: rgba(255, 255, 255, 0.04);
  --card-border: rgba(255, 255, 255, 0.08);
  --card-border-hover: rgba(110, 231, 242, 0.5);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.5;
}

#bg {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  display: block;
}

main {
  position: relative;
  z-index: 1;
}

.hero {
  min-height: 100svh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 2rem 1.5rem;
}

.eyebrow {
  margin: 0 0 0.5rem;
  color: var(--accent);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  font-size: 0.8rem;
  font-weight: 600;
}

.hero h1 {
  margin: 0;
  font-size: clamp(2.5rem, 8vw, 4.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.tagline {
  max-width: 38rem;
  margin: 1.25rem 0 0;
  color: var(--fg-dim);
  font-size: clamp(1rem, 2.5vw, 1.2rem);
}

.scroll-hint {
  margin-top: 3rem;
  color: var(--fg-dim);
  animation: bob 2s ease-in-out infinite;
  display: inline-flex;
}

.scroll-hint:hover {
  color: var(--accent);
}

@keyframes bob {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(6px); }
}

section {
  max-width: 42rem;
  margin: 0 auto;
  padding: 5rem 1.5rem;
}

section h2 {
  font-size: 1.6rem;
  margin: 0 0 1.25rem;
}

section p {
  color: var(--fg-dim);
  font-size: 1.05rem;
}

.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

.link-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
}

#breakdown {
  max-width: 64rem;
}

.section-intro {
  margin: -0.5rem 0 1.75rem;
}

.acronym-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 1rem;
}

.acronym-card {
  appearance: none;
  border: none;
  background: none;
  padding: 0;
  cursor: pointer;
  font: inherit;
  color: inherit;
  perspective: 1000px;
  aspect-ratio: 1;
}

.acronym-inner {
  position: relative;
  width: 100%;
  height: 100%;
  display: block;
  transform-style: preserve-3d;
  transition: transform 0.5s cubic-bezier(0.4, 0.2, 0.2, 1);
}

.acronym-card:hover .acronym-inner,
.acronym-card:focus-visible .acronym-inner,
.acronym-card.flipped .acronym-inner {
  transform: rotateY(180deg);
}

.acronym-face {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 0.75rem;
  border-radius: 0.75rem;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  backface-visibility: hidden;
  transition: border-color 0.25s ease, background 0.25s ease;
}

.acronym-card:hover .acronym-face,
.acronym-card:focus-visible .acronym-face,
.acronym-card.flipped .acronym-face {
  border-color: var(--card-border-hover);
  background: rgba(110, 231, 242, 0.06);
}

.acronym-letter {
  font-size: 2.25rem;
  font-weight: 700;
  color: var(--accent);
  line-height: 1;
}

.acronym-word {
  margin-top: 0.4rem;
  font-size: 0.85rem;
  color: var(--fg-dim);
}

.acronym-back {
  transform: rotateY(180deg);
  font-size: 0.85rem;
  color: var(--fg);
  line-height: 1.35;
}

.acronym-card:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
  border-radius: 0.75rem;
}

.link-card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  padding: 1.25rem 1.4rem;
  border-radius: 0.75rem;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  text-decoration: none;
  color: var(--fg);
  transition: border-color 0.25s ease, transform 0.25s ease, background 0.25s ease;
}

.link-card:hover,
.link-card:focus-visible {
  border-color: var(--card-border-hover);
  background: rgba(110, 231, 242, 0.06);
  transform: translateY(-3px);
}

.link-title {
  font-weight: 600;
  font-size: 1.05rem;
}

.link-desc {
  color: var(--fg-dim);
  font-size: 0.9rem;
}

footer {
  text-align: center;
  padding: 2rem 1.5rem 3rem;
  color: var(--fg-dim);
  font-size: 0.85rem;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  .scroll-hint {
    animation: none;
  }
  .reveal {
    transition: none;
  }
  .acronym-inner {
    transition: none;
  }
}