:root {
  color-scheme: dark;
  --background: #111111;
  --surface: #191919;
  --surface-hover: #202020;
  --text: #f2f2f0;
  --muted: #93938e;
  --line: #2b2b2b;
  --accent: #d5ff54;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--background);
  color: var(--text);
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

.home {
  width: min(100% - 40px, 720px);
  margin: 0 auto;
  padding: 90px 0 50px;
}

.home-header { margin-bottom: 85px; }

.brand-logo {
  width: 96px;
  height: 96px;
  display: block;
  margin-bottom: 36px;
  border-radius: 50%;
  object-fit: cover;
}

.home-header p,
.lesson-label {
  margin: 0 0 12px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 650;
  letter-spacing: .13em;
  text-transform: uppercase;
}

h1 {
  margin: 0;
  font-size: clamp(46px, 9vw, 78px);
  font-weight: 650;
  letter-spacing: -.055em;
  line-height: .98;
}

h2 {
  margin: 0;
  font-size: 15px;
  font-weight: 600;
  letter-spacing: -.01em;
}

.lesson-list > h2 {
  padding-bottom: 13px;
  border-bottom: 1px solid var(--line);
  color: var(--muted);
  font-size: 12px;
  letter-spacing: .08em;
  text-transform: uppercase;
}

.lesson-row {
  min-height: 90px;
  padding: 19px 5px;
  display: grid;
  grid-template-columns: 50px minmax(0, 1fr) auto;
  align-items: center;
  gap: 15px;
  border-bottom: 1px solid var(--line);
  text-decoration: none;
  transition: padding .15s ease, background .15s ease;
}

.lesson-row:hover {
  margin-inline: -14px;
  padding-inline: 19px;
  background: var(--surface-hover);
}

.lesson-number {
  color: var(--accent);
  font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
  font-size: 18px;
}

.lesson-info { min-width: 0; }
.lesson-info strong { display: block; font-size: 16px; font-weight: 600; }
.lesson-info small { display: block; overflow: hidden; color: var(--muted); font-size: 13px; text-overflow: ellipsis; white-space: nowrap; }
.arrow { color: var(--muted); font-size: 18px; }
.lesson-row:hover .arrow { color: var(--accent); }

.home footer {
  margin-top: 80px;
  color: #686864;
  font-size: 12px;
}

.lesson {
  width: min(100% - 40px, 720px);
  margin: 0 auto;
  padding: 30px 0 100px;
}

.lesson-nav { margin-bottom: 85px; display: flex; align-items: center; justify-content: space-between; }
.lesson-brand { width: 38px; height: 38px; display: block; border-radius: 50%; }
.lesson-brand img { display: block; width: 100%; height: 100%; border-radius: inherit; object-fit: cover; }
.lesson-nav a,
.back-link { color: var(--muted); font-size: 13px; text-decoration: none; }
.lesson-nav a:hover,
.back-link:hover { color: var(--text); }

.lesson-header {
  padding-bottom: 45px;
  border-bottom: 1px solid var(--line);
}

.lesson-header h1 {
  max-width: 680px;
  font-size: clamp(40px, 8vw, 64px);
  line-height: 1.05;
}

.lesson-intro {
  max-width: 600px;
  margin: 20px 0 0;
  color: var(--muted);
  font-size: 18px;
}

.lesson-content {
  padding: 28px 0 60px;
  font-size: 17px;
}

.lesson-content h2 {
  margin: 45px 0 12px;
  color: var(--text);
  font-size: 25px;
  letter-spacing: -.03em;
}

.lesson-content .group-heading {
  margin-top: 64px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  color: var(--accent);
  font-size: 14px;
  letter-spacing: .08em;
  text-transform: uppercase;
}

.lesson-content h3 {
  margin: 32px 0 8px;
  font-size: 19px;
}

.lesson-content p { margin: 0 0 22px; color: #d0d0cc; }
.lesson-content strong { color: var(--text); }
.lesson-content ul,
.lesson-content ol { margin: 0 0 24px; padding-left: 25px; color: #d0d0cc; }
.lesson-content li { margin: 8px 0; padding-left: 4px; }
.lesson-content a { color: var(--accent); text-underline-offset: 3px; }

.lesson-content blockquote {
  margin: 35px 0;
  padding: 17px 20px;
  border-left: 3px solid var(--accent);
  background: var(--surface);
  color: #d0d0cc;
}

.lesson-content hr { margin: 40px 0; border: 0; border-top: 1px solid var(--line); }
.lesson-content img { max-width: 100%; height: auto; margin: 24px 0; border-radius: 5px; }
.lesson-content code { padding: 2px 5px; border-radius: 4px; background: var(--surface); color: var(--accent); }
.lesson-content pre { overflow: auto; padding: 18px; border: 1px solid var(--line); border-radius: 5px; background: var(--surface); }
.lesson-content pre code { padding: 0; background: transparent; color: var(--text); }
.back-link { display: inline-block; padding-top: 25px; border-top: 1px solid var(--line); }

@media (max-width: 560px) {
  .home { width: calc(100% - 30px); padding-top: 50px; }
  .home-header { margin-bottom: 60px; }
  .brand-logo { width: 82px; height: 82px; margin-bottom: 30px; }
  h1 { font-size: 49px; }
  .lesson-row { grid-template-columns: 40px minmax(0, 1fr) auto; gap: 11px; }
  .lesson-row:hover { margin-inline: -7px; padding-inline: 12px; }
  .lesson { width: calc(100% - 30px); padding-top: 22px; }
  .lesson-nav { margin-bottom: 55px; }
  .lesson-header h1 { font-size: 42px; }
  .lesson-intro { font-size: 16px; }
  .lesson-content { font-size: 16px; }
}