:root {
  --bg: #0f1115;
  --bg-elevated: #161922;
  --border: #262a35;
  --text: #e6e8ec;
  --text-muted: #9aa1ae;
  --accent: #5eb3ff;
  --accent-strong: #8fcaff;
  --max-width: 780px;
  --header-height: 64px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
}

h1, h2, h3 {
  color: #fff;
  line-height: 1.25;
}

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

a:hover,
a:focus-visible {
  color: var(--accent-strong);
  text-decoration: underline;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--accent);
  color: #05131f;
  padding: 8px 16px;
  z-index: 100;
}

.skip-link:focus {
  left: 16px;
  top: 16px;
}

/* Header / nav */

.site-header {
  position: sticky;
  top: 0;
  height: var(--header-height);
  display: flex;
  align-items: center;
  background: rgba(15, 17, 21, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
  z-index: 10;
}

.nav {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  font-weight: 600;
  font-size: 1.05rem;
  color: #fff;
}

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

.nav-links {
  display: flex;
  gap: 28px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-links a {
  color: var(--text-muted);
  font-size: 0.95rem;
}

.nav-links a:hover,
.nav-links a:focus-visible {
  color: var(--text);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.nav-toggle span {
  width: 22px;
  height: 2px;
  background: var(--text);
}

/* Hero */

.hero {
  padding: 96px 24px 72px;
  scroll-margin-top: var(--header-height);
}

.eyebrow {
  margin: 0 0 4px;
  color: var(--accent);
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  font-size: 0.8rem;
}

.hero-text h1 {
  margin: 0 0 12px;
  font-size: 2.25rem;
}

.hero-subtitle {
  margin: 0 0 24px;
  color: var(--text-muted);
  max-width: 46ch;
}

.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  padding: 10px 20px;
  border-radius: 6px;
  font-weight: 500;
  font-size: 0.95rem;
}

.btn:hover,
.btn:focus-visible {
  text-decoration: none;
}

.btn-primary {
  background: var(--accent);
  color: #05131f;
}

.btn-primary:hover,
.btn-primary:focus-visible {
  background: var(--accent-strong);
  color: #05131f;
}

.btn-secondary {
  border: 1px solid var(--border);
  color: var(--text);
}

.btn-secondary:hover,
.btn-secondary:focus-visible {
  border-color: var(--accent);
  color: var(--accent);
}

/* Sections */

.section {
  padding: 56px 24px;
  border-top: 1px solid var(--border);
  scroll-margin-top: var(--header-height);
}

.section h2 {
  font-size: 1.5rem;
  margin: 0 0 20px;
}

.section p {
  color: var(--text-muted);
}

/* Education timeline */

.timeline {
  list-style: none;
  margin: 0;
  padding: 0;
  border-left: 2px solid var(--border);
}

.timeline-item {
  position: relative;
  padding: 0 0 28px 24px;
}

.timeline-item:last-child {
  padding-bottom: 0;
}

.timeline-item::before {
  content: "";
  position: absolute;
  left: -7px;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--bg);
}

.timeline-date {
  margin: 0 0 4px;
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 600;
}

.timeline-item h3 {
  margin: 0 0 4px;
  font-size: 1.05rem;
}

.timeline-item .meta {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* Tutorials */

.video-wrapper {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden;
  border-radius: 8px;
  border: 1px solid var(--border);
}

.video-wrapper iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

/* Footer */

.site-footer {
  border-top: 1px solid var(--border);
  padding: 48px 24px;
}

.footer-inner {
  text-align: center;
}

.footer-heading {
  margin: 0 0 16px;
  font-weight: 600;
  color: #fff;
}

.social-links {
  display: flex;
  justify-content: center;
  gap: 24px;
  list-style: none;
  margin: 0 0 24px;
  padding: 0;
}

.social-links a {
  color: var(--text-muted);
}

.social-links a:hover,
.social-links a:focus-visible {
  color: var(--accent);
}

.copyright {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* Responsive */

@media (max-width: 640px) {
  .nav-toggle {
    display: flex;
  }

  .nav-links {
    position: absolute;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    background: var(--bg-elevated);
    border-bottom: 1px solid var(--border);
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.2s ease;
  }

  .nav-links.open {
    max-height: 240px;
  }

  .nav-links li {
    border-top: 1px solid var(--border);
  }

  .nav-links a {
    display: block;
    padding: 14px 24px;
  }

  .hero {
    text-align: center;
    padding-top: 64px;
  }

  .hero-actions {
    justify-content: center;
  }
}