:root { --bg: #E7F7FC; --paper: #fff; --ink: #13335B; --soft: #4A6485; --link: #1E7FD8; --key: #F0FAFF; --line: #CDE6F3; }
@media (prefers-color-scheme: dark) {
  :root { --bg: #0E1C2E; --paper: #142740; --ink: #E6F0FA; --soft: #A9BDD3; --link: #6CB8FF; --key: #183252; --line: #24426A; }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 17px/1.6 system-ui, -apple-system, "Segoe UI", sans-serif; }
main { max-width: 760px; margin: 0 auto; padding: 24px 16px 48px; }
main > * { max-width: 70ch; }
h1 { font-size: 30px; line-height: 1.2; margin: 8px 0 4px; }
h2 { font-size: 20px; margin: 28px 0 8px; }
a { color: var(--link); }
ul { padding-left: 22px; }
li { margin: 6px 0; }
.muted { color: var(--soft); font-size: 15px; }
.back a { text-decoration: none; font-weight: 700; }
.key { background: var(--key); border: 1px solid var(--line); border-radius: 16px; padding: 4px 20px 8px; margin-top: 20px; }
.key h2 { margin-top: 16px; }
.foot { margin-top: 36px; }