:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #1c2430;
  --muted: #5d6b7c;
  --line: #dde2e8;
  --accent: #1f5fbf;
  --accent-text: #ffffff;
  --right: #1a7f4b;
  --right-bg: #e6f5ec;
  --wrong: #b3261e;
  --wrong-bg: #fbe9e7;
  --mark: #fff1a8;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12161c;
    --surface: #1b212a;
    --text: #e6eaf0;
    --muted: #9aa7b6;
    --line: #2e3744;
    --accent: #7db0ff;
    --accent-text: #0d1522;
    --right: #6fd39b;
    --right-bg: #173526;
    --wrong: #ff9a90;
    --wrong-bg: #3d1e1b;
    --mark: #6b5a00;
  }
}

* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 17px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
a { color: var(--accent); }
h1 { font-size: 1.7rem; line-height: 1.25; margin: 0 0 1rem; }
h2 { font-size: 1.15rem; margin: 0 0 .5rem; }
[hidden] { display: none !important; }
.muted { color: var(--muted); }
.small { font-size: .875rem; }

/* header */
.top { background: var(--surface); border-bottom: 1px solid var(--line); padding: .6rem 1rem; position: sticky; top: 0; z-index: 2; }
.top-row { max-width: 52rem; margin: 0 auto; display: flex; align-items: center; justify-content: space-between; gap: .75rem; flex-wrap: wrap; }
.top-row + .top-row { margin-top: .4rem; }
.brand { font-weight: 700; font-size: 1.15rem; color: var(--text); text-decoration: none; }
.who { font-size: .875rem; color: var(--muted); display: flex; gap: .6rem; align-items: center; }
#nav { display: flex; gap: .25rem; flex-wrap: wrap; }
#nav a { padding: .3rem .7rem; border-radius: 999px; text-decoration: none; color: var(--text); }
#nav a.active { background: var(--accent); color: var(--accent-text); }
#search { flex: 1 1 12rem; max-width: 20rem; }

main#view { max-width: 52rem; margin: 0 auto; padding: 1.5rem 1rem 4rem; }

/* form controls */
input[type="text"], input[type="password"], input[type="search"] {
  width: 100%; padding: .55rem .7rem; font: inherit; color: var(--text);
  background: var(--bg); border: 1px solid var(--line); border-radius: 8px;
}
input:focus-visible, button:focus-visible, a:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
button { font: inherit; cursor: pointer; }
button.primary { background: var(--accent); color: var(--accent-text); border: 0; border-radius: 8px; padding: .6rem 1.2rem; font-weight: 600; }
button.primary:disabled { opacity: .6; }
button.link { background: none; border: 0; padding: 0; color: var(--accent); text-decoration: underline; }

/* cards and lists */
.card { background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 1rem 1.25rem; margin: 0 0 1rem; }
.list { list-style: none; margin: 0; padding: 0; }
.list li { padding: .45rem 0; border-top: 1px solid var(--line); }
.list li:first-child { border-top: 0; }
.files li { display: flex; flex-wrap: wrap; gap: .25rem .9rem; align-items: baseline; }
.crumbs { color: var(--muted); font-size: .9rem; margin: 0 0 .75rem; }
.pager { display: flex; justify-content: space-between; gap: 1rem; margin-top: 2rem; padding-top: 1rem; border-top: 1px solid var(--line); }
.tag { margin-left: .6rem; font-size: .75rem; color: var(--muted); border: 1px solid var(--line); border-radius: 999px; padding: .05rem .5rem; white-space: nowrap; }
.results { list-style: none; margin: 0; padding: 0; }
.results p { margin: .35rem 0 0; }
mark { background: var(--mark); color: inherit; border-radius: 3px; padding: 0 .1em; }

/* notes */
.prose { overflow-wrap: break-word; }
.prose > :first-child { margin-top: 0; }
.prose > :last-child { margin-bottom: 0; }
.prose h1 { font-size: 1.7rem; }
.prose h2 { font-size: 1.3rem; margin: 1.75rem 0 .5rem; }
.prose h3 { font-size: 1.1rem; margin: 1.25rem 0 .4rem; }
.prose img { max-width: 100%; height: auto; border-radius: 8px; }
.prose table { border-collapse: collapse; display: block; overflow-x: auto; }
.prose th, .prose td { border: 1px solid var(--line); padding: .35rem .7rem; text-align: left; }
.prose blockquote { margin: 1rem 0; padding: .1rem 1rem; border-left: 4px solid var(--line); color: var(--muted); }
.prose code { background: var(--bg); border: 1px solid var(--line); border-radius: 4px; padding: .05em .3em; font-size: .9em; }
.prose pre { background: var(--bg); border: 1px solid var(--line); border-radius: 8px; padding: .8rem 1rem; overflow-x: auto; }
.prose pre code { border: 0; padding: 0; }

/* practice tests */
.q-num { font-size: .8rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); margin-bottom: .25rem; }
.question .prose { margin-bottom: .6rem; }
.option { display: flex; gap: .6rem; align-items: baseline; padding: .45rem .6rem; border: 1px solid var(--line); border-radius: 8px; margin-top: .4rem; cursor: pointer; }
.option.is-right { border-color: var(--right); background: var(--right-bg); }
.option.is-wrong { border-color: var(--wrong); background: var(--wrong-bg); }
.answer { max-width: 22rem; }
.feedback { margin-top: .8rem; padding-top: .7rem; border-top: 1px dashed var(--line); }
.feedback p { margin: .3rem 0; }
.right { color: var(--right); }
.wrong { color: var(--wrong); }
.got-right { border-color: var(--right); }
.got-wrong { border-color: var(--wrong); }
.score { font-size: 1.15rem; font-weight: 700; background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: .8rem 1.25rem; }

/* sign-in page */
.login-page { display: flex; min-height: 100vh; align-items: center; justify-content: center; padding: 1rem; }
.login-card { width: 100%; max-width: 26rem; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 1.75rem; }
.login-card h1 { margin-bottom: .25rem; }
.login-card label { display: block; font-weight: 600; font-size: .9rem; margin: 1rem 0 .3rem; }
.login-card button.primary { width: 100%; margin-top: 1.25rem; }
.login-card button.link { display: block; margin: .9rem auto 0; font-size: .9rem; }
.notice { background: var(--right-bg); color: var(--right); border-radius: 8px; padding: .5rem .75rem; margin: 1rem 0 0; font-size: .9rem; }
.error { color: var(--wrong); margin: .9rem 0 0; }