/* Decay Intelligence — academic/research site stylesheet
   Single accent: amethyst #a855f7 (VD brand family). Light page, generous whitespace.
   No pill buttons — interactive controls <= 5px border-radius. */

:root {
  --di-accent: #a855f7;
  --di-accent-dark: #6b3fa0;
  --di-bg: #fbfaf9;
  --di-bg-panel: #ffffff;
  --di-bg-muted: #f4f1f8;
  --di-text: #201c28;
  --di-text-muted: #5b5566;
  --di-border: #e4dfee;
  --di-code-bg: #f6f2fb;
  --di-serif: Georgia, 'Iowan Old Style', 'Palatino Linotype', Palatino, serif;
  --di-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
  --di-mono: ui-monospace, 'JetBrains Mono', SFMono-Regular, Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--di-bg);
  color: var(--di-text);
  font-family: var(--di-sans);
  line-height: 1.65;
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--di-accent-dark); text-decoration: none; border-bottom: 1px solid rgba(168,85,247,0.35); }
a:hover { color: var(--di-accent); border-bottom-color: var(--di-accent); }

h1, h2, h3, h4 {
  font-family: var(--di-serif);
  font-weight: 700;
  color: #14111a;
  line-height: 1.25;
  letter-spacing: -0.01em;
}

h1 { font-size: 2.4rem; margin: 0 0 0.5rem; }
h2 { font-size: 1.65rem; margin: 2.4rem 0 0.9rem; padding-top: 0.4rem; border-top: 1px solid var(--di-border); }
h2:first-of-type { border-top: none; padding-top: 0; }
h3 { font-size: 1.25rem; margin: 1.8rem 0 0.6rem; color: var(--di-accent-dark); }
p { margin: 0 0 1rem; }

.di-container { max-width: 880px; margin: 0 auto; padding: 0 24px; }

/* Header */
.di-header {
  background: var(--di-bg-panel);
  border-bottom: 1px solid var(--di-border);
}
.di-header-inner {
  max-width: 880px;
  margin: 0 auto;
  padding: 22px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}
.di-logo {
  font-family: var(--di-serif);
  font-weight: 700;
  font-size: 1.3rem;
  color: #14111a;
  border-bottom: none;
  letter-spacing: -0.01em;
}
.di-logo span { color: var(--di-accent); }
.di-tagline {
  font-family: var(--di-mono);
  font-size: 0.7rem;
  color: var(--di-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
}
.di-nav {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
}
.di-nav a {
  font-size: 0.9rem;
  color: var(--di-text-muted);
  border-bottom: 1px solid transparent;
}
.di-nav a:hover { color: var(--di-accent-dark); border-bottom-color: var(--di-accent); }

/* Hero / intro */
.di-hero {
  padding: 56px 0 24px;
  border-bottom: 1px solid var(--di-border);
  margin-bottom: 40px;
}
.di-hero .di-kicker {
  font-family: var(--di-mono);
  font-size: 0.75rem;
  color: var(--di-accent-dark);
  text-transform: uppercase;
  letter-spacing: 0.14em;
  display: block;
  margin-bottom: 14px;
}
.di-hero p.di-lede {
  font-size: 1.15rem;
  color: var(--di-text-muted);
  max-width: 680px;
}

main { padding-bottom: 40px; }

/* Card grid for index */
.di-card-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
  margin: 24px 0 40px;
}
@media (max-width: 640px) { .di-card-grid { grid-template-columns: 1fr; } }

.di-card {
  background: var(--di-bg-panel);
  border: 1px solid var(--di-border);
  border-radius: 5px;
  padding: 22px 24px;
  display: block;
  transition: border-color 0.15s ease, transform 0.15s ease;
}
.di-card:hover {
  border-color: var(--di-accent);
  transform: translateY(-1px);
}
.di-card h3 {
  margin: 0 0 8px;
  font-size: 1.1rem;
  color: #14111a;
}
.di-card p {
  margin: 0;
  font-size: 0.92rem;
  color: var(--di-text-muted);
}
.di-card .di-card-field {
  font-family: var(--di-mono);
  font-size: 0.68rem;
  color: var(--di-accent-dark);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  display: block;
  margin-bottom: 8px;
}

/* Formula blocks */
.di-formula {
  background: var(--di-code-bg);
  border: 1px solid var(--di-border);
  border-left: 3px solid var(--di-accent);
  border-radius: 4px;
  padding: 16px 20px;
  margin: 1.1rem 0;
  font-family: var(--di-mono);
  font-size: 0.95rem;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
}

code {
  font-family: var(--di-mono);
  background: var(--di-code-bg);
  padding: 0.1em 0.35em;
  border-radius: 3px;
  font-size: 0.9em;
}

/* Callout boxes */
.di-callout {
  border: 1px solid var(--di-border);
  border-left: 3px solid var(--di-accent-dark);
  background: var(--di-bg-muted);
  border-radius: 4px;
  padding: 16px 20px;
  margin: 1.4rem 0;
  font-size: 0.95rem;
}
.di-callout strong { color: var(--di-accent-dark); }

/* Tables */
table.di-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.4rem 0;
  font-size: 0.88rem;
}
table.di-table caption {
  text-align: left;
  font-family: var(--di-mono);
  font-size: 0.72rem;
  color: var(--di-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 8px;
}
table.di-table th, table.di-table td {
  border: 1px solid var(--di-border);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}
table.di-table th {
  background: var(--di-bg-muted);
  font-family: var(--di-sans);
  font-weight: 600;
  color: #14111a;
}
table.di-table td { color: var(--di-text-muted); }

/* Citations / source lists */
.di-sources {
  margin-top: 2.4rem;
  padding-top: 1.2rem;
  border-top: 1px solid var(--di-border);
}
.di-sources h2 { border-top: none; padding-top: 0; margin-top: 0; }
.di-sources ol {
  padding-left: 1.3rem;
  font-size: 0.9rem;
  color: var(--di-text-muted);
}
.di-sources li { margin-bottom: 0.5rem; }

/* Field article layout helpers */
.di-field-meta {
  font-family: var(--di-mono);
  font-size: 0.75rem;
  color: var(--di-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 1.6rem;
}

.di-glossary dt {
  font-family: var(--di-serif);
  font-weight: 700;
  color: var(--di-accent-dark);
  font-size: 1.05rem;
  margin-top: 1.4rem;
}
.di-glossary dd {
  margin: 0.3rem 0 0;
  color: var(--di-text-muted);
}

/* Back-to-index link */
.di-crumbs {
  font-family: var(--di-mono);
  font-size: 0.78rem;
  color: var(--di-text-muted);
  margin-bottom: 1.6rem;
}

/* Footer */
.di-footer {
  border-top: 1px solid var(--di-border);
  background: var(--di-bg-panel);
  margin-top: 40px;
}
.di-footer-inner {
  max-width: 880px;
  margin: 0 auto;
  padding: 32px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
  font-size: 0.85rem;
  color: var(--di-text-muted);
}
.di-footer-inner a { color: var(--di-text-muted); }
.di-footer-links { display: flex; gap: 16px; flex-wrap: wrap; }

ul.di-list { padding-left: 1.3rem; }
ul.di-list li { margin-bottom: 0.5rem; }