:root {
  /* StudentPay Brand Guidelines 2026 */
  --sp-dark-green: #286556;
  --sp-dark-green-hover: #1f4f43;
  --sp-dark-green-deep: #1a4339;
  --sp-lime: #71df78;
  --sp-lime-deep: #4fc857;
  --sp-indigo: #8b79f1; /* accent only — use sparingly */
  --sp-light-indigo: #d2caff; /* support panels only — use sparingly */
  --sp-black: #000000;
  --sp-white: #ffffff;

  --sp-text: #000000;
  --sp-body: #1a1a1a;
  --sp-muted: #4a5560;
  --sp-border: #d7dce2;
  --sp-panel: #f3f6f5;
  --sp-soft-green: #e7f2ee;

  --sp-font-display: "Poppins", "Segoe UI", sans-serif;
  --sp-font-sans: "Inter", "Segoe UI", sans-serif;
  --sp-font-mono: "IBM Plex Mono", ui-monospace, monospace;

  --sp-radius: 10px;
  --sp-sidebar: 280px;
  --sp-max: 1120px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--sp-font-sans);
  color: var(--sp-body);
  background:
    radial-gradient(1000px 420px at 100% 0%, rgba(113, 223, 120, 0.14), transparent 55%),
    linear-gradient(180deg, var(--sp-white) 0%, #f7faf8 50%, var(--sp-panel) 100%);
  min-height: 100vh;
  line-height: 1.6;
}

a {
  color: var(--sp-dark-green);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
}

a:hover {
  color: var(--sp-dark-green-hover);
}

.shell {
  display: grid;
  grid-template-columns: var(--sp-sidebar) minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  position: sticky;
  top: 0;
  align-self: start;
  height: 100vh;
  overflow: auto;
  padding: 1.5rem 1.25rem 2rem;
  border-right: 1px solid rgba(255, 255, 255, 0.08);
  background:
    linear-gradient(180deg, rgba(113, 223, 120, 0.1), transparent 34%),
    linear-gradient(180deg, var(--sp-dark-green) 0%, var(--sp-dark-green-deep) 100%);
  color: rgba(255, 255, 255, 0.88);
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
  margin-bottom: 1.75rem;
  text-decoration: none;
  color: inherit;
}

.brand-mark {
  font-family: var(--sp-font-display);
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--sp-white);
}

.brand-mark span {
  color: var(--sp-lime);
}

.brand-sub {
  font-size: 0.82rem;
  color: rgba(255, 255, 255, 0.68);
}

.nav-section {
  margin-bottom: 1.35rem;
}

.nav-section h2 {
  margin: 0 0 0.55rem;
  font-family: var(--sp-font-display);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.55);
}

.nav-section ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0.2rem;
}

.nav-section a {
  display: block;
  padding: 0.45rem 0.65rem;
  border-radius: 8px;
  color: rgba(255, 255, 255, 0.9);
  text-decoration: none;
  font-size: 0.95rem;
}

.nav-section a:hover {
  background: rgba(255, 255, 255, 0.1);
  color: var(--sp-white);
}

.nav-section a[aria-current="page"] {
  background: rgba(113, 223, 120, 0.22);
  color: var(--sp-white);
  font-weight: 600;
  box-shadow: inset 3px 0 0 var(--sp-lime);
}

.main {
  min-width: 0;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding: 0.9rem 1.5rem;
  border-bottom: 1px solid var(--sp-border);
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 5;
}

.topbar-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
  font-size: 0.9rem;
}

.topbar-links a {
  color: var(--sp-body);
  text-decoration: none;
  font-weight: 500;
}

.topbar-links a:hover {
  color: var(--sp-dark-green);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.25rem 0.65rem;
  border-radius: 999px;
  background: rgba(113, 223, 120, 0.22);
  color: var(--sp-dark-green);
  font-size: 0.78rem;
  font-weight: 600;
}

.content {
  max-width: var(--sp-max);
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
}

.prose h1 {
  margin: 0 0 0.75rem;
  font-family: var(--sp-font-display);
  font-size: clamp(1.9rem, 3vw, 2.45rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.03em;
  color: var(--sp-black);
}

.prose h2 {
  margin: 2rem 0 0.7rem;
  font-family: var(--sp-font-display);
  font-size: 1.35rem;
  font-weight: 600;
  color: var(--sp-black);
}

.prose h3 {
  margin: 1.4rem 0 0.5rem;
  font-family: var(--sp-font-display);
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--sp-black);
}

.prose p,
.prose ul,
.prose ol,
.prose table {
  margin: 0 0 1rem;
}

.prose li + li {
  margin-top: 0.25rem;
}

.prose strong {
  color: var(--sp-black);
}

.prose code {
  font-family: var(--sp-font-mono);
  font-size: 0.9em;
  background: var(--sp-soft-green);
  border: 1px solid rgba(40, 101, 86, 0.18);
  border-radius: 5px;
  padding: 0.08em 0.35em;
  color: var(--sp-black);
}

.prose pre {
  overflow: auto;
  padding: 1rem 1.1rem;
  border-radius: var(--sp-radius);
  background: #12251f;
  color: #f4f5f6;
  border: 1px solid #286556;
  margin: 0 0 1.2rem;
}

.prose pre code {
  background: transparent;
  border: 0;
  padding: 0;
  color: inherit;
  font-size: 0.88rem;
}

.prose table {
  width: 100%;
  border-collapse: collapse;
  overflow: hidden;
  border: 1px solid var(--sp-border);
  border-radius: var(--sp-radius);
  background: var(--sp-white);
}

.prose th,
.prose td {
  text-align: left;
  padding: 0.7rem 0.85rem;
  border-bottom: 1px solid var(--sp-border);
  vertical-align: top;
}

.prose th {
  background: var(--sp-soft-green);
  color: var(--sp-black);
  font-family: var(--sp-font-display);
  font-size: 0.86rem;
  font-weight: 600;
}

.prose tr:last-child td {
  border-bottom: 0;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.4rem 0 0.4rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.7rem 1.05rem;
  border-radius: 999px;
  font-family: var(--sp-font-sans);
  font-weight: 600;
  text-decoration: none;
  border: 1px solid transparent;
}

.btn-primary {
  background: var(--sp-dark-green);
  color: var(--sp-white);
}

.btn-primary:hover {
  background: var(--sp-dark-green-hover);
  color: var(--sp-white);
}

.btn-secondary {
  background: var(--sp-white);
  color: var(--sp-dark-green);
  border-color: var(--sp-dark-green);
}

.btn-secondary:hover {
  background: rgba(113, 223, 120, 0.18);
  border-color: var(--sp-lime-deep);
  color: var(--sp-dark-green-hover);
}

.footer-note {
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--sp-border);
  color: var(--sp-muted);
  font-size: 0.88rem;
}

.reference-frame {
  min-height: calc(100vh - 58px);
}

.reference-frame iframe,
.reference-frame #api-reference {
  min-height: calc(100vh - 58px);
  width: 100%;
}

.mobile-nav-toggle {
  display: none;
  border: 1px solid var(--sp-border);
  background: white;
  border-radius: 8px;
  padding: 0.4rem 0.65rem;
  font: inherit;
  color: var(--sp-black);
}

@media (max-width: 900px) {
  .shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    width: min(86vw, 300px);
    transform: translateX(-105%);
    transition: transform 0.2s ease;
    z-index: 20;
    box-shadow: 8px 0 30px rgba(0, 0, 0, 0.2);
  }

  body.nav-open .sidebar {
    transform: translateX(0);
  }

  .mobile-nav-toggle {
    display: inline-flex;
  }

  .backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.35);
    z-index: 15;
  }

  body.nav-open .backdrop {
    display: block;
  }
}