:root {
  /* The same colours as web/lab/lab.css and the course pages. */
  color-scheme: light dark;
  --bg: #f6f6f7;
  --surface: #fff;
  --text: #0b0b0c;
  --muted: #66666e;
  --accent: #12703a;
  --border: #e3e3e6;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0b0c;
    --surface: #141416;
    --text: #e8e8eb;
    --muted: #8d8d95;
    --accent: #22a861;
    --border: #27272b;
  }
}
* {
  box-sizing: border-box;
}
body {
  margin: 0;
  font:
    17px/1.65 system-ui,
    sans-serif;
  background: var(--bg);
  color: var(--text);
}
header,
main,
footer {
  max-width: 960px;
  margin: auto;
  padding: 24px;
}
header {
  display: flex;
  gap: 24px;
  justify-content: space-between;
  border-bottom: 1px solid var(--border);
}
nav {
  display: flex;
  gap: 20px;
}
a {
  color: var(--accent);
}
.brand {
  font-weight: 800;
  text-decoration: none;
  color: var(--text);
  font-size: 21px;
}
h1 {
  font-size: clamp(36px, 6vw, 66px);
  line-height: 1.1;
  letter-spacing: -0.04em;
  max-width: 800px;
  margin: 56px 0 24px;
}
h2 {
  font-size: 28px;
  line-height: 1.25;
}
.lead {
  font-size: 21px;
  color: var(--muted);
  max-width: 700px;
}
.card {
  padding: 28px;
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 16px;
  margin: 28px 0;
}
/* Home page: the two chapters side by side, buttons aligned at the bottom. */
.plans {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin: 40px 0;
}
.plans .card {
  margin: 0;
  display: flex;
  flex-direction: column;
}
.plans .card h2 {
  margin: 0;
}
.plans .button,
.plans button {
  margin-top: auto;
  text-align: center;
}
.plans .featured {
  border: 2px solid var(--accent);
}
.price {
  font-size: 40px;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1;
  margin: 16px 0 4px;
}
.price small {
  font-size: 17px;
  font-weight: 600;
  letter-spacing: 0;
  color: var(--muted);
}
.stages {
  list-style: none;
  padding: 0;
  margin: 8px 0 24px;
}
.stages li {
  padding: 8px 0;
  border-top: 1px solid var(--border);
}
.stages li::before {
  content: "✓";
  color: var(--accent);
  font-weight: 800;
  margin-right: 10px;
}
.tag {
  float: right;
  font-size: 12px;
  font-style: normal;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 99px;
  padding: 1px 8px;
}
.secondary {
  margin-top: 14px;
  font-size: 15px;
}
@media (max-width: 720px) {
  .plans {
    grid-template-columns: 1fr;
  }
}
.eyebrow {
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-weight: 700;
  color: var(--accent);
}
.button,
button {
  display: inline-block;
  border: 0;
  border-radius: 8px;
  background: var(--accent);
  color: var(--bg);
  padding: 12px 20px;
  font: inherit;
  font-weight: 650;
  text-decoration: none;
  cursor: pointer;
}
button:disabled {
  opacity: 0.6;
  cursor: wait;
}
input {
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px;
  font: inherit;
  width: 100%;
  margin: 8px 0 16px;
}
label {
  display: block;
}
form {
  max-width: 460px;
}
footer {
  font-size: 14px;
  color: var(--muted);
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
}
details {
  padding: 16px 0;
  border-bottom: 1px solid var(--border);
}
summary {
  cursor: pointer;
  font-weight: 650;
}
.muted {
  color: var(--muted);
}
#message {
  white-space: pre-line;
}
.danger {
  background: #a33131;
  color: white;
}
.plans .notify {
  margin-top: auto;
}