:root {
  --bg: #0f172a;
  --accent: #3b82f6;
  --accent-soft: rgba(59, 130, 246, 0.12);
  --accent-border: rgba(59, 130, 246, 0.6);
  --text: #e5e7eb;
  --muted: #9ca3af;
  --radius-pill: 999px;
  --shadow-soft: 0 18px 45px rgba(15, 23, 42, 0.8);
  --transition-fast: 0.18s ease-out;
  --border-subtle: 1px solid rgba(148, 163, 184, 0.15);
}

* {
  box-sizing: border-box;
}

html {
  font-size: 16px;
}

body {
  margin: 0;
  font-family: "Stack Sans Text", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: radial-gradient(circle at top, #1e293b 0, #020617 40%, #000 100%);
  background-attachment: fixed;
  color: var(--text);
  min-height: 100vh;
}

a {
  color: #93c5fd;
  text-underline-offset: 3px;
}

a:hover {
  color: #bfdbfe;
}

/* Top navigation */
.site-nav {
  max-width: 820px;
  margin-inline: auto;
  padding: 20px 16px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  font-size: 0.875rem;
}

.site-nav a {
  color: var(--muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.site-nav a:hover {
  color: var(--text);
}

.site-nav .brand {
  color: var(--text);
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.brand-dot {
  width: 8px;
  height: 8px;
  border-radius: 999px;
  background: radial-gradient(circle, var(--accent) 0, #22c55e 60%, transparent 100%);
}

.site-nav-links {
  display: flex;
  gap: 16px;
}

main {
  max-width: 820px;
  margin-inline: auto;
  padding: 24px 16px 40px;
}

@media (min-width: 768px) {
  main {
    padding: 32px 24px 56px;
  }
}

.card {
  background: linear-gradient(135deg, rgba(15, 23, 42, 0.96), rgba(15, 23, 42, 0.92));
  border-radius: 24px;
  padding: 24px 18px;
  border: var(--border-subtle);
  box-shadow: var(--shadow-soft);
  position: relative;
  overflow: hidden;
}

@media (min-width: 768px) {
  .card {
    padding: 40px 44px;
  }
}

.card::before {
  content: "";
  position: absolute;
  inset: -20%;
  background:
    radial-gradient(circle at 0 0, rgba(59, 130, 246, 0.16), transparent 55%),
    radial-gradient(circle at 100% 0, rgba(236, 72, 153, 0.12), transparent 55%);
  opacity: 0.24;
  pointer-events: none;
}

.card > * {
  position: relative;
}

/* Article typography */
.breadcrumb {
  font-size: 0.8rem;
  color: var(--muted);
  margin-bottom: 14px;
}

.breadcrumb a {
  color: var(--muted);
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 10px;
  border-radius: var(--radius-pill);
  background: rgba(148, 163, 184, 0.12);
  color: var(--muted);
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 12px;
}

h1 {
  font-size: clamp(1.75rem, 4vw, 2.4rem);
  line-height: 1.2;
  letter-spacing: -0.03em;
  margin: 0 0 12px;
}

.post-meta {
  color: var(--muted);
  font-size: 0.85rem;
  margin: 0 0 28px;
}

.lead {
  font-size: 1.075rem;
  color: #cbd5e1;
}

article h2 {
  font-size: 1.4rem;
  letter-spacing: -0.02em;
  margin: 40px 0 12px;
}

article h3 {
  font-size: 1.1rem;
  margin: 28px 0 8px;
}

article p,
article li {
  line-height: 1.75;
  color: #d1d5db;
}

article p {
  margin: 0 0 16px;
}

article ul,
article ol {
  padding-left: 22px;
  margin: 0 0 16px;
}

article li + li {
  margin-top: 6px;
}

article strong {
  color: var(--text);
}

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
  background: rgba(148, 163, 184, 0.12);
  padding: 1px 6px;
  border-radius: 6px;
}

/* Formula / worked example boxes */
.formula {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  background: rgba(2, 6, 23, 0.7);
  border: 1px solid rgba(148, 163, 184, 0.2);
  border-radius: 14px;
  padding: 14px 18px;
  margin: 0 0 18px;
  line-height: 1.9;
  overflow-x: auto;
  white-space: nowrap;
}

.example {
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  border-radius: 0 14px 14px 0;
  padding: 14px 18px;
  margin: 0 0 20px;
}

.example p:last-child {
  margin-bottom: 0;
}

.example-title {
  font-weight: 600;
  color: var(--text);
  margin-bottom: 6px !important;
}

.callout {
  border: 1px solid rgba(250, 204, 21, 0.35);
  background: rgba(250, 204, 21, 0.07);
  border-radius: 14px;
  padding: 14px 18px;
  margin: 0 0 20px;
}

.callout p:last-child {
  margin-bottom: 0;
}

/* Tables */
.table-wrap {
  overflow-x: auto;
  margin: 0 0 20px;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

th,
td {
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.15);
  white-space: nowrap;
}

th {
  color: var(--muted);
  font-weight: 500;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

td {
  color: #d1d5db;
}

/* Calculator call to action */
.cta {
  margin: 28px 0;
  padding: 20px;
  border-radius: 18px;
  border: 1px solid var(--accent-border);
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.14), rgba(139, 92, 246, 0.12));
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
}

.cta p {
  margin: 0;
  color: var(--text);
  flex: 1 1 260px;
}

.btn-primary {
  padding: 10px 20px;
  border-radius: var(--radius-pill);
  background: linear-gradient(135deg, #3b82f6, #8b5cf6);
  color: white;
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  box-shadow: 0 8px 22px rgba(59, 130, 246, 0.25);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), filter 0.12s ease-out;
}

.btn-primary:hover,
.btn-primary:focus {
  color: white;
  transform: translateY(-1px);
  box-shadow: 0 8px 22px rgba(59, 130, 246, 0.4);
  filter: brightness(1.05);
}

/* FAQ */
details {
  border: 1px solid rgba(148, 163, 184, 0.2);
  border-radius: 14px;
  padding: 12px 16px;
  margin-bottom: 10px;
  background: rgba(15, 23, 42, 0.6);
}

summary {
  cursor: pointer;
  font-weight: 500;
  color: var(--text);
}

details p {
  margin: 10px 0 0 !important;
}

/* Related posts */
.related {
  margin-top: 40px;
  padding-top: 24px;
  border-top: var(--border-subtle);
}

.related h2 {
  margin-top: 0;
  font-size: 1.1rem;
}

/* Blog index */
.page-header {
  text-align: center;
  margin-bottom: 28px;
}

.subtitle {
  margin: 0 auto;
  color: var(--muted);
  max-width: 560px;
  font-size: 0.95rem;
  line-height: 1.6;
}

.post-list {
  display: grid;
  gap: 16px;
}

.post-card {
  display: block;
  text-decoration: none;
  color: inherit;
  transition: transform var(--transition-fast), border-color var(--transition-fast);
}

.post-card:hover {
  color: inherit;
  transform: translateY(-2px);
  border-color: var(--accent-border);
}

.post-card h2 {
  font-size: 1.25rem;
  letter-spacing: -0.02em;
  margin: 0 0 8px;
}

.post-card p {
  color: var(--muted);
  line-height: 1.6;
  margin: 0 0 10px;
}

.post-card .post-meta {
  margin: 0;
  font-size: 0.8rem;
}

@media (min-width: 768px) {
  .post-card.card {
    padding: 28px 32px;
  }
}

/* Footer */
.site-footer {
  max-width: 820px;
  margin-inline: auto;
  padding: 0 16px 40px;
  text-align: center;
  color: var(--muted);
  font-size: 0.8rem;
}

.site-footer a {
  color: var(--muted);
}