:root {
  --ink: #0e1512;
  --surface: #16201c;
  --surface-2: #1b2723;
  --line: #26332c;
  --text: #e8f0ea;
  --muted: #8ca097;
  --faint: #5f7369;
  --mint: #3fd9a0;
  --sans: -apple-system, "Segoe UI", system-ui, Roboto, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--ink);
  color: var(--text);
  font-family: var(--sans);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
.wrap { max-width: 760px; margin: 0 auto; padding: 28px 24px 80px; }

/* nav */
nav {
  display: flex; align-items: center; justify-content: space-between;
  padding-bottom: 22px; margin-bottom: 30px; border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--text); }
.brand img { width: 26px; height: 26px; border-radius: 7px; }
.brand span { font-weight: 700; font-size: 16px; }
.nav-links { display: flex; gap: 18px; }
.nav-links a { color: var(--muted); text-decoration: none; font-size: 14px; }
.nav-links a:hover, .nav-links a.active { color: var(--mint); }

h1 { font-size: 32px; margin: 0 0 6px; letter-spacing: -0.01em; line-height: 1.25; }
h2 {
  font-size: 14px; margin: 34px 0 10px; color: var(--mint);
  letter-spacing: 0.06em; text-transform: uppercase;
}
h3 { font-size: 17px; margin: 26px 0 8px; }
p { margin: 0 0 14px; }
ul { margin: 0 0 14px; padding-left: 20px; }
li { margin-bottom: 8px; }
a { color: var(--mint); }
strong { color: var(--mint); font-weight: 600; }
.updated { color: var(--faint); font-size: 13px; margin: 0 0 30px; }
.lead {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: 12px; padding: 18px 20px; margin-bottom: 28px;
}
.lead p { margin: 0; font-size: 16px; }
.tagline { font-size: 19px; color: var(--muted); margin: 0 0 26px; }

.hero-img {
  width: 100%; border-radius: 14px; border: 1px solid var(--line);
  margin: 26px 0 8px; display: block;
}
.cta { display: flex; gap: 12px; flex-wrap: wrap; margin: 26px 0 10px; }
.btn {
  display: inline-block; padding: 11px 20px; border-radius: 10px;
  font-weight: 700; font-size: 15px; text-decoration: none;
}
.btn-primary { background: var(--mint); color: #06110c; }
.btn-ghost { border: 1px solid var(--line); color: var(--text); }
.btn-ghost:hover { border-color: var(--mint); }

.grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 8px 0 20px; }
.card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: 12px; padding: 16px 18px;
}
.card h4 { margin: 0 0 5px; font-size: 15px; }
.card p { margin: 0; font-size: 14px; color: var(--muted); }

.formula {
  background: var(--surface-2); border: 1px solid var(--line);
  border-radius: 12px; padding: 16px 18px; font-family: var(--mono);
  font-size: 13.5px; color: var(--muted); overflow-x: auto; margin-bottom: 14px;
}
.formula b { color: var(--mint); font-weight: 600; }

footer {
  margin-top: 46px; padding-top: 20px; border-top: 1px solid var(--line);
  color: var(--faint); font-size: 13px;
}
footer a { color: var(--muted); }

@media (max-width: 620px) {
  .grid { grid-template-columns: 1fr; }
  h1 { font-size: 26px; }
  .nav-links { gap: 12px; }
}