:root {
  --ink: #10284f;
  --ink-soft: #3a5278;
  --paper: #eef6ff;
  --paper-2: #ffffff;
  --line: #d4e4f7;
  --forest: #1547a8;
  --forest-2: #0d327c;
  --copper: #c88812;
  --focus: #0b5cab;
  --danger: #a1263a;
  --ok: #0f7a62;
  --shadow: 0 8px 24px rgba(21, 71, 168, 0.08);
  --max: 1120px;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
  --sans: "Segoe UI", "Helvetica Neue", Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(ellipse 55% 42% at 100% -8%, rgba(244, 186, 62, 0.38), transparent 48%),
    radial-gradient(ellipse 50% 40% at -8% 0%, rgba(47, 126, 232, 0.22), transparent 52%),
    var(--paper);
  font-family: var(--sans);
  font-size: 1.05rem;
  line-height: 1.55;
}

a { color: var(--forest); }

a:hover { color: var(--copper); }

img { max-width: 100%; }

.skip {
  position: absolute;
  left: 1rem;
  top: -4rem;
  background: var(--ink);
  color: white;
  padding: 0.5rem 0.8rem;
  z-index: 20;
}

.skip:focus { top: 0.5rem; }

.site-header {
  background: var(--paper-2);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 10;
}

.header-inner,
.wrap {
  width: min(var(--max), calc(100% - 2rem));
  margin-inline: auto;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 6.2rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  color: inherit;
  text-decoration: none;
}

.mark {
  height: 5.4rem;
  width: auto;
  max-width: min(46vw, 15.5rem);
  flex: none;
  display: block;
}

.brand-name {
  font-family: var(--serif);
  font-size: 1.15rem;
  letter-spacing: 0.01em;
  line-height: 1.15;
}

.brand-name span {
  display: block;
  font-family: var(--sans);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--copper);
}

.nav-toggle {
  display: none;
  border: 1px solid var(--line);
  background: var(--paper-2);
  padding: 0.45rem 0.7rem;
  font: inherit;
}

.nav {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav a {
  color: var(--ink);
  text-decoration: none;
  padding: 0.4rem 0.7rem;
  border-bottom: 2px solid transparent;
}

.nav a[aria-current="page"] {
  border-bottom-color: var(--forest);
  color: var(--forest);
}

.nav a.nav-solid {
  border-bottom: 0;
  border-radius: 8px;
}

.hero {
  display: grid;
  grid-template-columns: 1.4fr 0.8fr;
  gap: 2.5rem;
  align-items: center;
  padding: 3.8rem 0 2.8rem;
}

.symbol-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin: 1.2rem 0 0;
  padding: 0;
  list-style: none;
}

.symbol-row li {
  width: 2.4rem;
  height: 2.4rem;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  background: var(--paper-2);
  color: var(--forest);
  font-family: "Cambria Math", "Segoe UI Symbol", var(--serif);
  font-size: 1.25rem;
}

.kicker {
  margin: 0 0 0.6rem;
  color: var(--copper);
  font-size: 0.78rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

h1, h2, h3 { font-family: var(--serif); font-weight: 500; line-height: 1.15; }

h1 { font-size: clamp(2.2rem, 4vw, 3.4rem); margin: 0 0 0.8rem; }

h2 { font-size: 1.8rem; margin: 0 0 0.6rem; }

h3 { font-size: 1.25rem; margin: 0 0 0.4rem; }

.lede { font-size: 1.15rem; color: var(--ink-soft); max-width: 40rem; }

.hero-actions, .button-row { display: flex; flex-wrap: wrap; gap: 0.7rem; margin-top: 1.4rem; }

.button, button.button, .nav a.nav-solid {
  display: inline-block;
  border: 1px solid #24124f;
  border-radius: 10px;
  background: linear-gradient(180deg, #7a4de0 0%, #3146c8 48%, #1a216f 100%);
  color: white;
  text-decoration: none;
  padding: 0.65rem 1.05rem;
  font: inherit;
  cursor: pointer;
  text-shadow: 0 1px 0 rgba(18, 8, 46, 0.4);
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.48),
    inset 0 -3px 0 rgba(16, 8, 42, 0.35),
    0 4px 0 #140c38,
    0 9px 16px rgba(42, 24, 110, 0.28);
  transition: transform 0.12s ease, box-shadow 0.12s ease, background 0.12s ease;
}

.button:hover, button.button:hover, .nav a.nav-solid:hover {
  background: linear-gradient(180deg, #8b62ee 0%, #3d58dc 50%, #261c86 100%);
  color: white;
  transform: translateY(-1px);
}

.button:active, button.button:active, .nav a.nav-solid:active {
  transform: translateY(3px);
  box-shadow:
    inset 0 3px 6px rgba(12, 6, 32, 0.45),
    0 1px 0 #140c38;
}

.button.secondary {
  background: linear-gradient(180deg, #ffffff 0%, #f4f0ff 100%);
  color: #2a1870;
  border-color: #6d46c8;
  text-shadow: none;
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.9),
    0 3px 0 #d9cef5,
    0 6px 12px rgba(42, 24, 110, 0.12);
}

.button.secondary:hover {
  background: linear-gradient(180deg, #8b62ee 0%, #3d58dc 50%, #261c86 100%);
  color: white;
  border-color: #24124f;
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.48),
    0 4px 0 #140c38,
    0 9px 16px rgba(42, 24, 110, 0.28);
}

.button:disabled, button.button:disabled {
  transform: none;
  opacity: 0.6;
  cursor: default;
}

.figure {
  background:
    linear-gradient(180deg, #ffffff 0%, #f3f8ff 100%);
  color: var(--ink);
  border: 1px solid #efd48a;
  min-height: 0;
  padding: 0.8rem 1rem 1.1rem;
  display: grid;
  justify-items: center;
  gap: 0.4rem;
  box-shadow: 0 18px 40px rgba(21, 71, 168, 0.14);
}

.figure img { width: min(100%, 280px); height: auto; }

.figure p { margin: 0; font-size: 0.98rem; text-align: center; color: var(--ink-soft); }

.figure p.motto {
  font-weight: 700;
  letter-spacing: 0.01em;
  background-image: linear-gradient(90deg, #7a0614, #e10600, #ff6b6b, #ffd6d6, #c8102e, #7a0614);
  background-size: 220% 100%;
  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;
  animation: motto-run 4.5s linear infinite;
}

@keyframes motto-run {
  from { background-position: 0% 50%; }
  to { background-position: 220% 50%; }
}

@media (prefers-reduced-motion: reduce) {
  .figure p.motto { animation: none; }
}

.band {
  background: var(--paper-2);
  border-block: 1px solid var(--line);
}

.steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1rem;
  padding: 2rem 0 2.4rem;
}

.step {
  border-top: 2px solid var(--forest);
  padding-top: 0.8rem;
}

.step span {
  display: block;
  color: var(--copper);
  font-size: 0.8rem;
  letter-spacing: 0.08em;
}

.section { padding: 2.6rem 0; }

.qualification { margin-bottom: 2.2rem; }

.igcse-pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  align-items: start;
  margin-bottom: 2.2rem;
}

.igcse-pair .qualification { margin-bottom: 0; }

.igcse-pair .cards { grid-template-columns: 1fr; }

.igcse-pair .card { min-height: 0; }

.qualification header {
  margin-bottom: 1rem;
  max-width: 46rem;
  padding-bottom: 0.8rem;
  border-bottom: 1px solid var(--line);
}

.meta {
  color: var(--ink-soft);
  margin: 0;
}

.cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}

.card {
  background: var(--paper-2);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  padding: 1.1rem 1.1rem 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  min-height: 100%;
  position: relative;
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}

.card:hover {
  transform: translateY(-3px);
  box-shadow: 0 14px 30px rgba(21, 71, 168, 0.12);
}

.glyph {
  position: absolute;
  top: 0.85rem;
  right: 0.95rem;
  color: var(--copper);
  font-family: "Cambria Math", "Segoe UI Symbol", var(--serif);
  font-size: 1.35rem;
  line-height: 1;
}

.card p { margin: 0; color: var(--ink-soft); flex: 1; }

.code {
  align-self: flex-start;
  border: 1px solid var(--line);
  padding: 0.1rem 0.45rem;
  font-size: 0.75rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.card a.more { font-weight: 600; }

.page-head { padding: 2.4rem 0 0.4rem; }

.crumb { color: var(--ink-soft); font-size: 0.92rem; }

.crumb a { color: inherit; }

.detail {
  display: grid;
  grid-template-columns: 1.5fr 0.8fr;
  gap: 1.5rem;
  padding-bottom: 3rem;
}

.panel {
  background: var(--paper-2);
  border: 1px solid var(--line);
  padding: 1.1rem 1.2rem;
}

.panel ul, .outline { margin: 0.4rem 0 0; padding-left: 1.15rem; }

.form {
  display: grid;
  gap: 0.85rem;
  max-width: 32rem;
}

label { display: grid; gap: 0.3rem; font-weight: 600; }

input, textarea, select {
  font: inherit;
  padding: 0.55rem 0.65rem;
  border: 1px solid #c9bfb0;
  background: white;
  color: var(--ink);
  width: 100%;
}

textarea { min-height: 8rem; resize: vertical; }

input:focus, textarea:focus, button:focus, a:focus {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

.note, .banner {
  background: #e7f0ea;
  border-left: 3px solid var(--ok);
  padding: 0.8rem 1rem;
}

.banner.warn {
  background: #f8efe6;
  border-left-color: var(--copper);
}

.error { color: var(--danger); margin: 0; }

.site-footer {
  border-top: 1px solid var(--line);
  padding: 1.4rem 0 2rem;
  color: var(--ink-soft);
  font-size: 0.92rem;
}

.site-footer .wrap {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.table-wrap { overflow-x: auto; margin: 1rem 0 2rem; }

table.records {
  width: 100%;
  border-collapse: collapse;
  background: var(--paper-2);
}

table.records th,
table.records td {
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--line);
  padding: 0.7rem 0.5rem;
}

table.records th {
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink-soft);
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.45rem;
}

.button.small {
  padding: 0.35rem 0.55rem;
  font-size: 0.9rem;
  border-radius: 8px;
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.42),
    inset 0 -2px 0 rgba(16, 8, 42, 0.3),
    0 2px 0 #140c38,
    0 5px 10px rgba(42, 24, 110, 0.22);
}

.button.quiet {
  background: linear-gradient(180deg, #ffffff, #f7f5ff);
  color: #2a1870;
  border-color: #d7cef0;
  text-shadow: none;
  box-shadow: 0 2px 0 #e4def4;
}

.button.quiet:hover {
  background: linear-gradient(180deg, #7a4de0 0%, #3146c8 48%, #1a216f 100%);
  color: white;
  border-color: #24124f;
}

.dates {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.dates label { font-size: 0.82rem; min-width: 9rem; }

.pay-select { width: auto; min-width: 7.5rem; }

.work-box { display: grid; gap: 0.55rem; margin-top: 0.8rem; }

.work-box textarea, .review-grid textarea { min-height: 5.5rem; }

.working {
  white-space: pre-wrap;
  max-height: 12rem;
  overflow: auto;
  margin: 0.4rem 0 0.7rem;
  padding: 0.6rem 0.7rem;
  background: white;
  border: 1px solid var(--line);
}

.review-grid { display: grid; gap: 0.55rem; margin-top: 0.4rem; }

.check-line { margin: 0.35rem 0; }

details.lesson-check { margin: 0.35rem 0 0.8rem; }

details.lesson-check summary { cursor: pointer; font-weight: 600; }

.stack { display: grid; gap: 1rem; padding-bottom: 3rem; }

.lesson-block { margin: 0 0 1.4rem; }

.lesson-block h2 { margin-top: 1.6rem; }

.lesson-links { margin: 0.2rem 0 0.85rem; padding-left: 1.2rem; }

.lesson-links li { margin: 0.28rem 0; }

.lesson-links a.quiet-link { margin-left: 0.7rem; font-size: 0.92rem; }

.closed-label {
  margin-left: 0.45rem;
  color: var(--copper);
  font-size: 0.75rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.note-block { margin: 0.8rem 0; }

.math-figure {
  margin: 1rem 0;
  padding: 0.6rem;
  background: white;
  border: 1px solid #efd48a;
  display: grid;
  justify-items: center;
  gap: 0.4rem;
}

.math-figure img, .math-figure svg { width: min(100%, 520px); height: auto; }

.pdf-page {
  margin: 0 auto 1.2rem;
  max-width: 860px;
  background: white;
  border: 1px solid #efd48a;
  box-shadow: 0 16px 36px rgba(21, 71, 168, 0.12);
  padding: 0.6rem 0.6rem 0.8rem;
}

.pdf-page img {
  width: 100%;
  height: auto;
  display: block;
  background: white;
}

.pdf-page figcaption {
  margin-top: 0.45rem;
  text-align: right;
  color: var(--ink-soft);
  font-size: 0.85rem;
}

.math-figure figcaption { color: var(--ink-soft); font-size: 0.92rem; }

.callout {
  background: #fff;
  border: 1px solid #e4d4fb;
  border-left: 5px solid #5b2d91;
  border-radius: 12px;
  padding: 0.85rem 1rem 0.3rem;
  box-shadow: 0 10px 24px rgba(70, 28, 120, 0.08);
}

.callout.hint,
.callout.extra {
  border-left-color: #c88812;
  background: linear-gradient(180deg, #fffdf8, #fff6e8);
}

.callout .kicker { color: #5b2d91; }

.lesson-table {
  width: 100%;
  border-collapse: collapse;
  background: white;
}

.lesson-table th {
  background: linear-gradient(180deg, #6a3cbc, #3a1578);
  color: #f8e7b0;
  letter-spacing: 0.04em;
}

.lesson-table td, .lesson-table th {
  border: 1px solid #e4d4fb;
  text-align: center;
  padding: 0.45rem 0.55rem;
}

.lesson-table tbody tr:nth-child(even) { background: #faf7ff; }

.marks {
  color: #c88812;
  font-size: 0.9rem;
}

.paper-ref {
  margin: 0.35rem 0 0;
  text-align: right;
  color: #5b2d91;
  font-size: 0.86rem;
}

.question { margin: 0 0 1rem; }

.answer { margin-top: 0.45rem; }

.katex-display { overflow-x: auto; overflow-y: hidden; padding-bottom: 0.2rem; }

.lesson-switch { display: flex; flex-wrap: wrap; gap: 0.6rem; margin: 0.8rem 0 1rem; }

.video-frame { width: 100%; margin: 0.8rem 0 1rem; }
.video-frame iframe { width: 100%; aspect-ratio: 16 / 9; border: 0; background: #10284f; }

@media (max-width: 900px) {
  .hero, .detail, .cards, .steps { grid-template-columns: 1fr 1fr; }
  .steps { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 700px) {
  .nav-toggle { display: inline-block; }

  .nav {
    display: none;
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    background: var(--paper-2);
    border-bottom: 1px solid var(--line);
    flex-direction: column;
    align-items: stretch;
    padding: 0.4rem 1rem 0.8rem;
  }

  .nav.is-open { display: flex; }

  .hero, .detail, .cards, .steps, .igcse-pair { grid-template-columns: 1fr; }

  .mark { height: 4.2rem; }
  .header-inner { min-height: 5.2rem; }
}