/* ZetaZero — clean, plain stylesheet */

:root {
  --bg: #ffffff;
  --text: #222222;
  --muted: #666666;
  --line: #e5e5e5;
  --green: #168a45;
  --green-dark: #0f6f38;
  --max-width: 760px;
}

* { box-sizing: border-box; }
html { -webkit-font-smoothing: antialiased; text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Arial, Helvetica, sans-serif;
  font-size: 17px;
  line-height: 1.65;
}

a { color: var(--text); text-decoration: underline; text-underline-offset: 3px; }
a:hover { color: var(--green-dark); }
a:focus-visible { outline: 2px solid var(--green); outline-offset: 3px; }

.page, header.site, footer.site {
  width: min(var(--max-width), calc(100% - 40px));
  margin-left: auto;
  margin-right: auto;
}

header.site {
  padding: 28px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  border-bottom: 1px solid var(--line);
}

.site-mark {
  color: var(--text);
  font-size: 16px;
  font-weight: 700;
  text-decoration: none;
}
.site-mark:hover { color: var(--green-dark); }
.site-mark .qed { margin-left: 3px; color: var(--green); }

nav.site-nav { display: flex; gap: 22px; flex-wrap: wrap; }
nav.site-nav a { color: var(--muted); text-decoration: none; }
nav.site-nav a:hover,
nav.site-nav a[aria-current="page"] { color: var(--text); text-decoration: underline; }

.hero { padding: 55px 0 40px; }
.eyebrow {
  margin: 0 0 12px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: .04em;
  text-transform: uppercase;
}
h1.title { margin: 0 0 14px; font-size: clamp(2.3rem, 6vw, 3.5rem); line-height: 1.1; font-weight: 700; }
.subtitle { max-width: 650px; margin: 0 0 30px; color: var(--muted); font-size: 1.05rem; }

.abstract { padding: 22px 0 5px; border-top: 1px solid var(--line); }
.abstract .label { display: block; margin-bottom: 8px; color: var(--muted); font-size: 12px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; }
.abstract p { margin: 0 0 12px; }

section.sec { padding: 34px 0; border-top: 1px solid var(--line); }
.sec-head { display: flex; align-items: baseline; gap: 10px; margin-bottom: 12px; }
.sec-num { color: var(--muted); font-size: 14px; }
h2.sec-title { margin: 0; font-size: 1.35rem; font-weight: 700; }
.sec ul.plain { margin: 0; padding-left: 20px; }
.sec ul.plain li { padding: 2px 0; }

.coffee-button {
  display: inline-block;
  margin-top: 8px;
  padding: 11px 20px;
  background: var(--green);
  color: #fff;
  border: 1px solid var(--green);
  border-radius: 5px;
  font-weight: 700;
  text-decoration: none;
}
.coffee-button:hover { background: var(--green-dark); border-color: var(--green-dark); color: #fff; }

.entry { padding: 28px 0; border-top: 1px solid var(--line); }
.entry:first-of-type { border-top: none; }
.entry-head { display: flex; align-items: baseline; justify-content: space-between; gap: 16px; margin-bottom: 8px; }
.entry-title { margin: 0; font-size: 1.3rem; font-weight: 700; }
.entry-title .n { margin-right: 9px; color: var(--muted); font-size: 14px; font-weight: 400; }
.entry-title a { color: var(--text); text-decoration: none; }
.entry-title a:hover { color: var(--green-dark); text-decoration: underline; }
.entry-links { display: flex; gap: 18px; flex-wrap: wrap; font-size: 14px; }
.entry-links a { color: var(--green-dark); font-weight: 600; }

footer.site {
  margin-top: 30px;
  padding: 24px 0 50px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
}
footer.site a { color: var(--muted); }

@media (max-width: 560px) {
  body { font-size: 16px; }
  header.site { align-items: flex-start; flex-direction: column; }
  .page, header.site, footer.site { width: min(var(--max-width), calc(100% - 28px)); }
  .hero { padding-top: 38px; }
}