:root {
  color-scheme: dark;
  --bg: #080b0e;
  --panel: #11181e;
  --line: #2a353e;
  --cyan: #69ffe2;
  --pink: #ff60ca;
  --muted: #a7b3bd;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: 25px;
}

body {
  margin: 0;
  background: var(--bg);
  color: #f5f5ef;
  font: 17px/1.65 system-ui, sans-serif;
}

a { color: inherit; }

header {
  max-width: 1280px;
  margin: auto;
  padding: 24px 32px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--line);
}

.brand {
  text-decoration: none;
  font-size: 28px;
  font-weight: 900;
  color: var(--cyan);
  display: flex;
  align-items: center;
  gap: 20px;
}

.brand span {
  font: 10px monospace;
  letter-spacing: 2px;
  color: white;
}

main {
  max-width: 1280px;
  margin: auto;
  padding: 0 32px;
}

.hero {
  display: grid;
  grid-template-columns: 1.2fr .8fr;
  gap: 70px;
  align-items: center;
  padding: 60px 0 80px;
}

.eyebrow {
  font: 11px/1.6 monospace;
  letter-spacing: 2px;
  color: var(--cyan);
}

h1 {
  font-size: clamp(46px, 5.5vw, 78px);
  line-height: 1.04;
  letter-spacing: -4px;
  margin: 22px 0;
}

h1 em {
  font-style: normal;
  color: var(--cyan);
}

.intro {
  color: var(--muted);
  font-size: 20px;
}

.button,
button {
  font: inherit;
  cursor: pointer;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 12px 18px;
  background: var(--panel);
  color: white;
}

.button {
  display: inline-flex;
  gap: 50px;
  background: var(--cyan);
  color: #071511;
  text-decoration: none;
  font-weight: 700;
  margin-top: 15px;
}

.facts {
  display: flex;
  gap: 20px;
  margin-top: 28px;
  font: 11px monospace;
  color: var(--muted);
}

figure { margin: 0; }

.hero-card {
  transform: rotate(2deg);
  max-width: 390px;
  justify-self: end;
  box-shadow: 0 0 100px #51d5b715;
}

.hero-card img {
  width: 100%;
  display: block;
  border-radius: 12px;
  border: 1px solid #467b76;
}

figcaption {
  font: 10px monospace;
  letter-spacing: 2px;
  padding: 14px;
  color: var(--muted);
}

h2 {
  font-size: 30px;
  line-height: 1.2;
  letter-spacing: -1px;
}

.section-head {
  display: flex;
  justify-content: space-between;
  align-items: end;
}

#progress {
  font: 12px monospace;
  color: var(--cyan);
}

#lesson-nav {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin: 22px 0;
}

#lesson-nav button {
  text-align: left;
  padding: 20px;
}

#lesson-nav button[aria-current="true"] {
  border-color: var(--cyan);
  background: #152923;
}

#lesson-nav small {
  display: block;
  color: var(--muted);
  font: 11px monospace;
  margin-bottom: 8px;
}

.workspace {
  display: grid;
  grid-template-columns: 1.35fr 1fr;
  gap: 28px;
}

article,
aside,
.quiz {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 30px;
  background: var(--panel);
}

article h2 { margin-top: 12px; }
article p { color: #c5ced5; }

.dialogue {
  border-left: 2px solid var(--pink);
  padding: 0 0 0 20px;
  margin: 25px 0;
}

.dialogue b {
  font: 11px monospace;
  color: var(--pink);
  display: block;
  letter-spacing: 1px;
}

.dialogue p { margin: 5px 0 20px; }

.example {
  border: 1px solid #38675b;
  border-radius: 5px;
  padding: 16px;
  color: var(--cyan) !important;
}

label {
  display: block;
  font-size: 13px;
  margin: 18px 0 8px;
}

input {
  width: 100%;
  background: #070c10;
  color: white;
  border: 1px solid #54616b;
  border-radius: 5px;
  padding: 12px;
  font: 20px monospace;
}

#lab-result {
  border-top: 1px solid var(--line);
  margin-top: 25px;
  padding-top: 20px;
}

#lab-result strong {
  font-size: 36px;
  color: var(--cyan);
  display: block;
}

#lab-result.negative strong { color: #ff96bb; }

.small {
  font-size: 12px;
  color: var(--muted);
}

.quiz { margin: 28px 0; }

#answers {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

#answers button[aria-pressed="true"] {
  border-color: var(--cyan);
}

#feedback {
  min-height: 28px;
  color: var(--cyan);
}

.collection {
  padding: 60px 0;
  border-bottom: 1px solid var(--line);
}

#cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-top: 30px;
}

.mini-card {
  padding: 24px;
  border: 1px solid #48746d;
  border-radius: 10px;
  background: linear-gradient(150deg, #172a29, #181124);
  display: flex;
  flex-direction: column;
  min-height: 290px;
}

.mini-card small {
  font: 10px monospace;
  color: var(--cyan);
}

.mini-card h3 {
  font-size: 25px;
  line-height: 1.2;
}

.mini-card blockquote {
  margin: 0;
  color: var(--pink);
  font-size: 18px;
}

.mini-card p {
  font-size: 13px;
  color: var(--muted);
}

.mini-card .copyright {
  margin-top: auto;
  font-size: 9px;
}

.notes {
  max-width: 700px;
  padding: 45px 0;
}

footer {
  border-top: 1px solid var(--line);
  padding: 30px;
  text-align: center;
  font: 10px/2 monospace;
  color: var(--muted);
}

button:hover { border-color: var(--cyan); }

:focus-visible {
  outline: 3px solid var(--pink);
  outline-offset: 4px;
}

.skip {
  position: absolute;
  top: -100px;
}

.skip:focus {
  top: 10px;
  background: black;
  padding: 10px;
  z-index: 3;
}

@media (max-width: 760px) {
  header,
  main {
    padding-left: 20px;
    padding-right: 20px;
  }

  .brand span {
    max-width: 120px;
    line-height: 1.4;
  }

  .hero {
    grid-template-columns: 1fr;
    gap: 40px;
    padding: 35px 0;
  }

  .hero-card {
    max-width: 310px;
    justify-self: center;
  }

  h1 { letter-spacing: -2px; }
  .workspace { grid-template-columns: 1fr; }
  #lesson-nav { grid-template-columns: 1fr; }
  #cards { grid-template-columns: 1fr; }
  .section-head { display: block; }

  article,
  aside,
  .quiz { padding: 22px; }

  .facts { gap: 12px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}