/* ============================================================
   OxbridgeAI — Outclass design system
   Monochrome Swiss / International Typographic Style.
   Mirrors Outclass-school-agency OutclassLanding.tsx +
   docs/design/2026-06-21-outclass-frontend-design-system.md.
   Paper + ink, IBM Plex, hairline rules, artefact frames,
   Klein blue (#002FA7) as the single minimal accent.
   ============================================================ */

:root {
  --paper: #f4f3ee;
  --surface: #ffffff;
  --ink: #111111;
  --ink2: #3a3a38;
  --ink3: #6b6a64;
  --hair: #cfcdc4;
  --hair2: #d8d6ce;
  --klein: #002fa7;
  --klein-hover: #0a2ecc;
  --klein-wash: #eceefb;
  --sans: "IBM Plex Sans", -apple-system, BlinkMacSystemFont, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, monospace;
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

::selection {
  background: var(--ink);
  color: var(--paper);
}

body {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-weight: 400;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1,
h2,
h3,
h4 {
  font-family: var(--sans);
  font-weight: 600;
}

a {
  color: inherit;
}

/* ── Layout ── */
.wrap {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 40px;
}
.wrap-sm {
  max-width: 820px;
  margin: 0 auto;
  padding: 0 40px;
}
@media (max-width: 700px) {
  .wrap,
  .wrap-sm {
    padding: 0 24px;
  }
}

/* ── Mono helpers ── */
.mono {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

/* ── Section rhythm ── */
.section {
  padding: 80px 0;
}
.section.tight {
  padding: 60px 0;
}
.section.invert {
  background: var(--ink);
  color: var(--paper);
}

.section-label {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 12px;
  color: var(--ink);
  border-top: 1px solid var(--ink);
  padding-top: 14px;
  margin-bottom: 28px;
}
.section.invert .section-label {
  color: var(--paper);
  border-top-color: #333;
}

.eyebrow {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 12px;
  color: var(--ink);
}

/* ── Typography ── */
.display {
  font-size: clamp(2.5rem, 5.5vw, 3.5rem);
  line-height: 1.04;
  font-weight: 600;
  letter-spacing: -0.025em;
}
.h2 {
  font-size: clamp(1.9rem, 3.4vw, 2.4rem);
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.12;
}
.h3 {
  font-size: 1.25rem;
  font-weight: 500;
  line-height: 1.3;
}
.lead {
  font-size: 1.0625rem;
  line-height: 1.6;
  color: var(--ink2);
}
.muted {
  color: var(--ink3);
}
.underline-ink {
  border-bottom: 4px solid var(--ink);
  padding-bottom: 4px;
  display: inline-block;
}
.klein {
  color: var(--klein);
}

/* ── Buttons ── */
.btn {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 12px;
  padding: 13px 22px;
  display: inline-block;
  text-decoration: none;
  cursor: pointer;
  border: 1px solid transparent;
  transition:
    opacity 0.2s ease,
    background 0.2s ease,
    color 0.2s ease;
}
.btn-primary {
  background: var(--ink);
  color: #fff;
  border-color: var(--ink);
}
.btn-primary:hover {
  opacity: 0.82;
}
.btn-outline {
  background: transparent;
  color: var(--ink);
  border-color: var(--ink);
}
.btn-outline:hover {
  background: var(--ink);
  color: #fff;
}
.btn-klein {
  background: var(--klein);
  color: #fff;
  border-color: var(--klein);
}
.btn-klein:hover {
  background: var(--klein-hover);
}
.section.invert .btn-outline {
  color: var(--paper);
  border-color: var(--paper);
}
.section.invert .btn-outline:hover {
  background: var(--paper);
  color: var(--ink);
}
.section.invert .btn-primary {
  background: var(--paper);
  color: var(--ink);
  border-color: var(--paper);
}

/* ── NAV ── */
#nav {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(244, 243, 238, 0.86);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--ink);
}
.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 18px 40px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.nav-logo {
  display: flex;
  align-items: center;
  gap: 11px;
  text-decoration: none;
  color: var(--ink);
}
.nav-logo .emblem {
  font-size: 1.7rem;
  line-height: 1;
  font-weight: 600;
}
.nav-logo .emblem-img {
  height: 26px;
  width: auto;
  display: block;
}
.footer-logo .emblem-img {
  height: 20px;
  width: auto;
  display: block;
}
.nav-logo .wordmark {
  font-size: 1.5rem;
  font-weight: 600;
  letter-spacing: -0.015em;
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 26px;
  list-style: none;
}
.nav-links a {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 12px;
  color: var(--ink);
  text-decoration: none;
  transition: color 0.2s;
}
.nav-links a:hover {
  color: var(--klein);
}
.nav-links a.active {
  color: var(--klein);
}
.nav-right {
  display: flex;
  align-items: center;
  gap: 22px;
}

.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  border: 1px solid var(--ink);
  background: transparent;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
  cursor: pointer;
}
.nav-toggle span {
  width: 18px;
  height: 1.5px;
  background: var(--ink);
}
.nav-mobile {
  display: none;
  flex-direction: column;
  padding: 8px 40px 20px;
  background: var(--paper);
  border-bottom: 1px solid var(--ink);
}
.nav-mobile.open {
  display: flex;
}
.nav-mobile a {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 12px;
  color: var(--ink);
  text-decoration: none;
  padding: 13px 0;
  border-top: 1px solid var(--hair);
}

@media (max-width: 820px) {
  .nav-inner {
    padding: 16px 24px;
  }
  .nav-links {
    display: none;
  }
  .nav-right .btn {
    display: none;
  }
  .nav-toggle {
    display: flex;
  }
  .nav-mobile {
    padding: 8px 24px 20px;
  }
}

/* ── Page hero (interior pages) ── */
.page-hero {
  padding: 70px 0 50px;
}
.page-hero .eyebrow {
  display: block;
  margin-bottom: 22px;
}
.page-hero-title {
  font-size: clamp(2.4rem, 5vw, 3.25rem);
  font-weight: 600;
  letter-spacing: -0.025em;
  line-height: 1.05;
  max-width: 20ch;
}
.page-hero-sub {
  font-size: 1.0625rem;
  line-height: 1.6;
  color: var(--ink2);
  max-width: 38rem;
  margin-top: 22px;
}

/* ── Artefact / bordered frame ── */
.artefact {
  border: 1px solid var(--ink);
  background: var(--surface);
}
.artefact-bar {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 11px;
  color: #fff;
  background: var(--ink);
  padding: 8px 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.artefact-bar .live {
  color: var(--klein);
  text-transform: none;
  letter-spacing: 0.05em;
}
.artefact-body {
  padding: 16px;
}

/* ── Cards (agents / features) ── */
.card-grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
@media (max-width: 820px) {
  .card-grid-3 {
    grid-template-columns: 1fr;
    max-width: 460px;
  }
}
.oc-card {
  border: 1px solid var(--ink);
  background: var(--surface);
  height: 100%;
  transition: transform 0.25s ease;
}
.oc-card:hover {
  transform: translateY(-4px);
}
.oc-card-bar {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 11px;
  color: #fff;
  background: var(--ink);
  padding: 8px 14px;
}
.oc-card-body {
  padding: 18px 16px 22px;
}
.oc-card-body h3 {
  font-size: 1.125rem;
  font-weight: 500;
  line-height: 1.25;
}
.oc-card-body p {
  font-size: 0.875rem;
  color: var(--ink2);
  line-height: 1.55;
  margin-top: 12px;
}

/* ── Hairline column row (how-it-works / stats) ── */
.rule-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  border-top: 1px solid var(--ink);
  padding-top: 28px;
  margin-top: 8px;
}
@media (max-width: 700px) {
  .rule-row {
    grid-template-columns: 1fr;
    gap: 28px;
  }
}
.rule-col {
  padding: 0 28px;
  border-left: 1px solid var(--hair);
}
.rule-col:first-child {
  border-left: none;
  padding-left: 0;
}
@media (max-width: 700px) {
  .rule-col {
    border-left: none;
    padding: 0;
  }
}

/* ── Stat (big number + mono caption) ── */
.stat-num {
  font-family: var(--sans);
  font-size: clamp(2.2rem, 4vw, 2.75rem);
  font-weight: 600;
  letter-spacing: -0.03em;
  line-height: 1;
}
.stat-cap {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 11px;
  color: var(--ink3);
  margin-top: 12px;
  line-height: 1.5;
}

/* ── Checklist (trust / features) ── */
.checklist {
  max-width: 40rem;
}
.check-row {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 0;
  border-top: 1px solid var(--hair);
  font-size: 1rem;
  color: var(--ink);
}
.check-row .tick {
  flex-shrink: 0;
  width: 18px;
  height: 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--klein);
  font-weight: 700;
}

/* ── Prose (blog / guide / legal) ── */
.prose {
  font-size: 1.0625rem;
  color: var(--ink2);
  line-height: 1.75;
}
.prose > * + * {
  margin-top: 22px;
}
.prose h2 {
  font-size: clamp(1.6rem, 2.6vw, 2rem);
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--ink);
  margin-top: 52px;
  line-height: 1.2;
}
.prose h3 {
  font-size: 1.3rem;
  font-weight: 600;
  color: var(--ink);
  margin-top: 40px;
}
.prose h4 {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 0.72rem;
  color: var(--ink3);
  margin-top: 36px;
}
.prose a {
  color: var(--klein);
  text-decoration: underline;
  text-underline-offset: 3px;
}
.prose a:hover {
  color: var(--klein-hover);
}
.prose strong {
  color: var(--ink);
  font-weight: 600;
}
.prose ul,
.prose ol {
  padding-left: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.prose ul li,
.prose ol li {
  padding-left: 24px;
  position: relative;
  line-height: 1.7;
}
.prose ul li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 11px;
  width: 10px;
  height: 1px;
  background: var(--ink);
}
.prose ol {
  counter-reset: ol;
}
.prose ol li {
  counter-increment: ol;
}
.prose ol li::before {
  content: counter(ol, decimal-leading-zero);
  position: absolute;
  left: 0;
  top: 1px;
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--klein);
}
.prose blockquote {
  font-size: 1.25rem;
  color: var(--ink);
  line-height: 1.5;
  padding-left: 22px;
  border-left: 2px solid var(--ink);
  margin: 8px 0;
  font-weight: 500;
}
.prose table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}
.prose th,
.prose td {
  text-align: left;
  padding: 13px 16px;
  border-bottom: 1px solid var(--hair);
}
.prose th {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink3);
}
.prose img {
  max-width: 100%;
  height: auto;
  display: block;
}

/* ── FAQ accordion ── */
.faq-list {
  border-bottom: 1px solid var(--hair);
}
.faq-item {
  border-top: 1px solid var(--hair);
}
.faq-q {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  padding: 20px 0;
  background: none;
  border: none;
  cursor: pointer;
  text-align: left;
  font-family: var(--sans);
  font-size: 1.125rem;
  font-weight: 500;
  color: var(--ink);
}
.faq-q::after {
  content: "+";
  font-family: var(--mono);
  font-size: 1.1rem;
  color: var(--ink3);
  flex-shrink: 0;
}
.faq-item.open .faq-q::after {
  content: "–";
}
.faq-a {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s ease;
}
.faq-a-inner {
  font-size: 0.9375rem;
  color: var(--ink2);
  line-height: 1.6;
  padding-bottom: 22px;
  max-width: 44rem;
}
.faq-a-inner a {
  color: var(--klein);
}

/* ── Forms ── */
.field {
  margin-bottom: 20px;
}
.field-label {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 11px;
  color: var(--ink3);
  display: block;
  margin-bottom: 8px;
}
.field-input,
.field-textarea,
.field-select {
  width: 100%;
  background: var(--surface);
  border: 1px solid var(--ink);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 1rem;
  padding: 13px 14px;
  outline: none;
  transition:
    box-shadow 0.15s,
    border-color 0.15s;
}
.field-input:focus,
.field-textarea:focus,
.field-select:focus {
  border-color: var(--klein);
  box-shadow: 0 0 0 2px var(--klein-wash);
}
.field-input::placeholder,
.field-textarea::placeholder {
  color: var(--ink3);
}
.field-textarea {
  resize: vertical;
  min-height: 130px;
}
.form-success {
  display: none;
  font-family: var(--mono);
  letter-spacing: 0.08em;
  font-size: 0.8rem;
  color: var(--klein);
  margin-top: 18px;
}

/* ── Footer ── */
footer {
  border-top: 1px solid var(--ink);
}
.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 28px 40px;
  flex-wrap: wrap;
  gap: 18px;
  max-width: 1200px;
  margin: 0 auto;
}
.footer-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--ink);
}
.footer-logo .emblem {
  font-size: 1.2rem;
  font-weight: 600;
}
.footer-logo .wordmark {
  font-size: 0.95rem;
  font-weight: 600;
}
.footer-links {
  display: flex;
  gap: 22px;
  list-style: none;
  flex-wrap: wrap;
}
.footer-links a {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 11px;
  color: var(--ink3);
  text-decoration: none;
  transition: color 0.2s;
}
.footer-links a:hover {
  color: var(--ink);
}
.footer-meta {
  font-family: var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-size: 11px;
  color: var(--ink3);
}

/* ── Scroll reveal ── */
.up {
  opacity: 0;
  transform: translateY(26px);
}
.up.shown {
  opacity: 1;
  transform: translateY(0);
  transition:
    opacity 0.65s cubic-bezier(0.22, 1, 0.36, 1),
    transform 0.65s cubic-bezier(0.22, 1, 0.36, 1);
}
@media (prefers-reduced-motion: reduce) {
  .up {
    opacity: 1;
    transform: none;
  }
}