/* Maths Solver — base stylesheet
   Minimal, content-first. One accent color. System fonts where possible. */

:root {
  --bg: #fffefb;
  --text: #1a1a1a;
  --muted: #5b5b5b;
  --line: #e5e3de;
  --accent: #c2410c;
  --accent-hover: #9a3412;
  --code-bg: #f5f3ee;

  --serif: Charter, "Bitstream Charter", "Sitka Text", Cambria, Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, system-ui, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 17px/1.65 var(--serif);
  font-feature-settings: "kern", "liga", "onum";
  -webkit-font-smoothing: antialiased;
}

img, svg { max-width: 100%; height: auto; display: block; }

/* Layout wrappers */
.wrap     { max-width: 720px; margin: 0 auto; padding: 0 22px; }
.wrap-wide { max-width: 880px; margin: 0 auto; padding: 0 22px; }

/* Links */
a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 2px;
  text-decoration-thickness: 1px;
}
a:hover { color: var(--accent-hover); text-decoration-thickness: 2px; }

/* Header / nav */
.site-header {
  border-bottom: 1px solid var(--line);
  padding: 14px 0;
  font-family: var(--sans);
}
.site-header .wrap-wide {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 24px;
  flex-wrap: wrap;
}
.site-header .brand,
a.brand {
  display: inline-flex !important;
  flex-direction: row !important;
  align-items: center;
  gap: 9px;
  white-space: nowrap;
  font-weight: 600;
  color: var(--text);
  text-decoration: none;
  font-size: 17px;
  letter-spacing: -0.005em;
  line-height: 1;
}
.brand:hover { color: var(--accent); }
.site-header .brand-logo,
.brand-logo {
  width: 26px !important;
  height: 26px !important;
  flex-shrink: 0;
  vertical-align: middle;
  display: inline-block !important;
  object-fit: contain;
  margin: 0 !important;
}
.site-nav { display: flex; gap: 20px; }
.site-nav a {
  color: var(--text);
  text-decoration: none;
  font-size: 15px;
}
.site-nav a:hover { color: var(--accent); }
.site-nav a.current { color: var(--accent); }

/* Headings (default for article body) */
h1, h2, h3, h4 {
  font-family: var(--serif);
  font-weight: 600;
  letter-spacing: -0.01em;
  line-height: 1.25;
  margin: 1.6em 0 0.5em;
}
h1 { font-size: clamp(1.7rem, 4vw, 2.3rem); margin-top: 0; }
h2 { font-size: 1.45rem; }
h3 { font-size: 1.15rem; }

p { margin: 0 0 1.05em; }

/* Article body */
article { padding: 0 0 60px; }
article p, article li { font-size: 17px; }
article ul, article ol { padding-left: 1.4em; margin: 0 0 1.2em; }
article li { margin-bottom: 0.4em; }
article hr { border: none; border-top: 1px solid var(--line); margin: 40px 0; }

article blockquote {
  margin: 1.4em 0;
  padding: 4px 0 4px 18px;
  border-left: 3px solid var(--accent);
  color: var(--muted);
  font-style: italic;
}

article code {
  font-family: var(--mono);
  font-size: 0.92em;
  background: var(--code-bg);
  padding: 1px 5px;
  border-radius: 3px;
}

/* Page header for articles */
.article-header {
  padding: 50px 0 24px;
}
.breadcrumb {
  font-family: var(--sans);
  font-size: 13px;
  color: var(--muted);
  margin: 0 0 14px;
}
.breadcrumb a { color: var(--muted); }
.breadcrumb a:hover { color: var(--accent); }

.article-meta {
  font-family: var(--sans);
  font-size: 14px;
  color: var(--muted);
  margin: 12px 0 0;
}
.article-meta a { color: var(--text); text-decoration: none; border-bottom: 1px solid var(--line); }
.article-meta a:hover { color: var(--accent); border-color: var(--accent); }

/* Section labels (small caps style headers used on home) */
.section-label {
  font-family: var(--sans);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  border-bottom: 1px solid var(--line);
  padding-bottom: 8px;
  margin: 0 0 18px;
  font-weight: 600;
}

/* Embedded calculator widget — secondary, not the star */
.calc {
  margin: 32px 0;
  padding: 22px;
  border: 1px solid var(--line);
  background: #fbfaf6;
  border-radius: 4px;
  font-family: var(--sans);
}
.calc h4 {
  font-family: var(--sans);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  margin: 0 0 12px;
}
.calc-row { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.calc input[type="text"], .calc input[type="number"] {
  font: 15px var(--mono);
  padding: 9px 12px;
  border: 1px solid var(--line);
  border-radius: 3px;
  background: #fff;
  color: var(--text);
  outline: none;
  flex: 1;
  min-width: 0;
}
.calc input:focus { border-color: var(--accent); }
.calc label { font-size: 14px; color: var(--muted); margin-right: 4px; }
.calc button {
  font: 500 14px var(--sans);
  padding: 9px 16px;
  background: var(--text);
  color: #fff;
  border: none;
  border-radius: 3px;
  cursor: pointer;
}
.calc button:hover { background: var(--accent); }
.calc-output {
  margin-top: 16px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  font-family: var(--serif);
  font-size: 15.5px;
  color: var(--text);
  display: none;
}
.calc-output.show { display: block; }
.calc-output .step { margin: 0.6em 0; }
.calc-output .step strong { color: var(--accent); font-family: var(--sans); font-size: 12px; text-transform: uppercase; letter-spacing: 0.06em; display: block; margin-bottom: 2px; }
.calc-output .err { color: #b91c1c; }
.calc-note { font-size: 13px; color: var(--muted); margin: 10px 0 0; }

/* Author byline card (article footer) */
.author-card {
  margin: 50px 0 0;
  padding: 22px 0;
  border-top: 1px solid var(--line);
  display: flex;
  gap: 16px;
  align-items: flex-start;
  font-family: var(--sans);
}
.author-card .avatar {
  width: 48px; height: 48px; flex-shrink: 0;
  border-radius: 50%;
}
.author-card h4 {
  font-family: var(--sans); font-size: 15px; margin: 0 0 4px; font-weight: 600;
}
.author-card p { font-size: 14px; color: var(--muted); margin: 0; line-height: 1.5; }
.author-card a { color: var(--text); }
.author-card a:hover { color: var(--accent); }

/* References list */
.references {
  font-family: var(--sans);
  font-size: 14px;
  color: var(--muted);
}
.references li { margin-bottom: 0.5em; }
.references a { color: var(--text); }

/* Footer */
.site-footer {
  border-top: 1px solid var(--line);
  margin-top: 60px;
  padding: 30px 0 36px;
  font-family: var(--sans);
  font-size: 14px;
  color: var(--muted);
}
.site-footer .wrap-wide {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  flex-wrap: wrap;
}
.site-footer a { color: var(--muted); text-decoration: none; }
.site-footer a:hover { color: var(--accent); }
.site-footer nav { display: flex; gap: 14px; flex-wrap: wrap; }

/* Inline figure for SVG diagrams */
figure.diagram {
  margin: 28px 0;
  text-align: center;
}
figure.diagram svg { margin: 0 auto; display: block; }
figure.diagram img {
  max-width: 100%;
  height: auto;
  margin: 0 auto;
  display: block;
  border-radius: 4px;
  border: 1px solid var(--line);
}
figure.diagram figcaption {
  font-family: var(--sans);
  font-size: 13px;
  color: var(--muted);
  margin-top: 8px;
}

/* MathJax tweaks — keep inline math from breaking lines awkwardly */
mjx-container { overflow-x: auto; overflow-y: hidden; }
mjx-container[display="true"] { margin: 1em 0; }

/* Mobile */
@media (max-width: 640px) {
  body { font-size: 16.5px; }
  .site-header .wrap-wide { flex-direction: column; align-items: flex-start; gap: 10px; }
  .site-nav { gap: 14px; flex-wrap: wrap; }
  .site-footer .wrap-wide { flex-direction: column; }
  .article-header { padding: 30px 0 18px; }
  .calc { padding: 16px; }
  .author-card { flex-direction: column; }
}