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

:root {
  --bg: #0a0a0a;
  --fg: #e0e0e0;
  --muted: #888;
  --accent: #4ade80;
  --accent-dim: #22633a;
  --surface: #141414;
  --border: #222;
  --yt-red: #ff0000;
}

html {
  font-size: 18px;
}

body {
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.landing {
  max-width: 640px;
  margin: 0 auto;
  padding: 4rem 1.5rem 3rem;
}

/* Hero */

.hero {
  margin-bottom: 3rem;
}

.hero h1 {
  font-size: 2.8rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  color: #fff;
  margin-bottom: 0.3rem;
}

.tagline {
  color: var(--muted);
  font-size: 1.1rem;
}

/* Sections */

section {
  margin-bottom: 2.5rem;
}

h2 {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.8rem;
}

p {
  margin-bottom: 0.8rem;
  color: var(--fg);
}

p:last-child {
  margin-bottom: 0;
}

strong {
  color: #fff;
  font-weight: 600;
}

/* YouTube link */

.yt-link {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  color: #fff;
  text-decoration: none;
  font-weight: 600;
  font-size: 1.15rem;
  padding: 0.7rem 1.2rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  transition: border-color 0.2s, background 0.2s;
  margin-top: 0.5rem;
}

.yt-link:hover {
  border-color: var(--yt-red);
  background: #1a0a0a;
  text-decoration: none;
}

.yt-icon {
  width: 28px;
  height: 20px;
  flex-shrink: 0;
}

/* Inline links */

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* Architecture — brain layers */

.brain-layer,
.infra-item {
  margin-bottom: 1.8rem;
}

.brain-layer h3,
.infra-item h3 {
  font-size: 1rem;
  font-weight: 600;
  color: #fff;
  margin-bottom: 0.4rem;
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
}

.repo-link {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-family: "SF Mono", "Fira Code", "Fira Mono", Menlo, Consolas, monospace;
  font-size: 0.8rem;
  font-weight: 400;
  color: var(--muted);
  margin-left: 0.5rem;
}

.repo-link:hover {
  color: var(--accent);
  text-decoration: none;
}

.gh-icon {
  width: 14px;
  height: 14px;
  flex-shrink: 0;
}

.brain-interaction {
  margin-top: 2rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}

.brain-interaction h3 {
  font-size: 1rem;
  font-weight: 600;
  color: #fff;
  margin-bottom: 0.6rem;
}

.github {
  margin-bottom: 0;
}

/* GitHub link */

.gh-link {
  display: inline-block;
  color: #fff;
  font-weight: 600;
  font-size: 1.05rem;
  padding: 0.7rem 1.2rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  transition: border-color 0.2s, background 0.2s;
  text-decoration: none;
}

.gh-link:hover {
  border-color: var(--accent);
  background: #0a1a0f;
  text-decoration: none;
}

/* Footer */

.footer {
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}

.footer p {
  color: var(--muted);
  font-style: italic;
  font-size: 0.9rem;
}

/* Responsive */

@media (max-width: 480px) {
  html {
    font-size: 16px;
  }

  .landing {
    padding: 2.5rem 1.2rem 2rem;
  }

  .hero h1 {
    font-size: 2.2rem;
  }
}