:root {
  color-scheme: light;
  --paper: #f4f5ef;
  --surface: #fffefa;
  --ink: #192c29;
  --muted: #65736e;
  --line: #dce2da;
  --green: #147d67;
  --green-dark: #0e5b4d;
  --green-pale: #e5f1eb;
  --coral: #e9785d;
  --yellow: #edc75f;
  --shadow: 0 10px 34px rgba(24, 47, 41, .06);
  font-family: "Manrope", sans-serif;
  color: var(--ink);
  background: var(--paper);
  font-synthesis: none;
  text-rendering: optimizeLegibility;
}

* { box-sizing: border-box; }
body { margin: 0; min-width: 320px; background: var(--paper); }
a { color: inherit; }
button { font: inherit; }

.topbar {
  min-height: 70px;
  padding: 0 clamp(20px, 6vw, 92px);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 254, 250, .76);
}
.brand { display: inline-flex; align-items: center; gap: 11px; text-decoration: none; font-size: 14px; font-weight: 600; }
.brand strong { font-weight: 800; }
.brand-mark { display: grid; place-items: center; width: 34px; aspect-ratio: 1; border-radius: 9px; color: white; background: var(--green); font-family: Georgia, serif; font-size: 22px; }
.topbar-meta { display: flex; align-items: center; gap: 9px; color: var(--muted); font-size: 12px; }
.status-dot { width: 7px; aspect-ratio: 1; border-radius: 50%; background: var(--coral); }
.admin-link { text-decoration: none; color: var(--green-dark); font-size: 12px; font-weight: 700; }
.admin-link span { margin-left: 4px; }

main { max-width: 1180px; margin: 0 auto; padding: 0 34px; }
.intro { min-height: 340px; padding: 58px 0 50px; display: flex; align-items: center; justify-content: space-between; gap: 40px; position: relative; }
.intro::after { content: ""; position: absolute; width: 188px; height: 188px; border: 1px solid rgba(20, 125, 103, .17); border-radius: 50%; right: 42px; top: 32px; pointer-events: none; }
.intro-copy { position: relative; z-index: 1; max-width: 710px; animation: rise-in .55s ease both; }
.eyebrow { margin: 0 0 12px; color: var(--green); font: 500 10px/1.4 "DM Mono", monospace; letter-spacing: 0; }
h1 { margin: 0; font-size: clamp(37px, 5vw, 58px); line-height: 1.08; font-weight: 800; letter-spacing: 0; }
h1 span { display: block; color: var(--green); }
.intro-text { max-width: 550px; margin: 18px 0 0; color: var(--muted); font-size: 14px; line-height: 1.8; }
.contact-button { min-height: 44px; margin-top: 22px; padding: 0 17px; display: inline-flex; align-items: center; gap: 12px; border-radius: 3px; color: white; background: var(--green-dark); font-size: 12px; font-weight: 800; text-decoration: none; transition: background .18s, transform .18s; }
.contact-button:hover { background: var(--green); transform: translateY(-1px); }
.contact-button span { font-size: 15px; }
.intro-note { z-index: 1; width: 205px; min-height: 190px; padding: 15px; display: flex; flex-direction: column; align-items: flex-start; justify-content: space-between; border: 0; border-left: 2px solid var(--coral); border-radius: 0; background: transparent; box-shadow: none; transform: none; animation: rise-in .65s .12s ease both; }
.note-label, .note-caption { color: var(--muted); font: 500 9px/1.7 "DM Mono", monospace; }
.teacher-initials { color: var(--green); font-size: 60px; line-height: 1; font-weight: 800; }

.library { padding: 30px clamp(18px, 4vw, 42px) 40px; border: 1px solid var(--line); border-radius: 5px; background: var(--surface); box-shadow: var(--shadow); animation: rise-in .65s .18s ease both; }
.library-heading { display: flex; align-items: end; justify-content: space-between; gap: 20px; padding-bottom: 23px; border-bottom: 1px solid var(--line); }
.library-heading .eyebrow { margin-bottom: 7px; }
.library-hint { margin: 6px 0 0; color: var(--muted); font-size: 11px; line-height: 1.6; }
h2 { margin: 0; font-size: 23px; line-height: 1.3; letter-spacing: 0; }
.content-count { padding-bottom: 3px; color: var(--muted); font: 11px "DM Mono", monospace; white-space: nowrap; }
.breadcrumbs { min-height: 55px; display: flex; align-items: center; gap: 9px; border-bottom: 1px solid var(--line); color: var(--muted); font-size: 11px; }
.crumb { padding: 5px 0; border: 0; color: inherit; background: transparent; cursor: pointer; }
.crumb.active { color: var(--green-dark); font-weight: 800; cursor: default; }
.crumb:not(.active):hover { color: var(--green); }
.crumb-separator { color: #a8b2aa; font-family: "DM Mono", monospace; }
.level-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; padding-top: 20px; }
.level-item { min-height: 78px; padding: 15px 17px; display: flex; align-items: center; gap: 14px; border: 1px solid var(--line); border-radius: 3px; color: var(--ink); text-align: left; background: #fff; cursor: pointer; transition: border-color .18s, background .18s, transform .18s; }
.level-item:hover { border-color: #9dc6b5; background: #fbfefa; transform: translateY(-1px); }
.item-index { display: grid; flex: 0 0 34px; place-items: center; width: 34px; aspect-ratio: 1; border-radius: 50%; color: var(--green-dark); background: var(--green-pale); font: 11px "DM Mono", monospace; }
.item-copy { min-width: 0; flex: 1; }
.item-title { display: block; font-size: 13px; font-weight: 700; line-height: 1.5; }
.item-subtitle { display: block; margin-top: 3px; color: var(--muted); font-size: 10px; }
.item-arrow { color: var(--green); font-size: 17px; }
.exercise-list { display: grid; gap: 15px; padding-top: 22px; }
.exercise { overflow: hidden; border: 1px solid var(--line); border-radius: 3px; background: #fff; }
.exercise-header { display: flex; align-items: center; gap: 12px; padding: 16px 19px; border-bottom: 1px solid var(--line); background: #fbfcf8; }
.exercise-tag { padding: 5px 8px; border-radius: 2px; color: var(--green-dark); background: var(--green-pale); font: 10px "DM Mono", monospace; }
.exercise-header h3 { margin: 0; font-size: 14px; line-height: 1.5; }
.exercise-body { padding: 6px 20px 20px; }
.exercise-section { padding-top: 14px; font-size: 13px; line-height: 1.8; }
.exercise-section h4 { margin: 0 0 6px; color: var(--green-dark); font: 500 10px "DM Mono", monospace; }
.exercise-section p { margin: 7px 0; }
.exercise-section ol { margin: 7px 0; padding-left: 20px; }
.exercise-section li { margin: 5px 0; }
.exercise-section mjx-container[display="true"] { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.figure { max-width: 100%; height: auto; display: block; margin: 14px auto 3px; border: 1px solid var(--line); }
.exercise-actions { margin-top: 17px; padding-top: 13px; display: flex; flex-wrap: wrap; gap: 16px; border-top: 1px solid var(--line); }
.exercise-actions a { color: var(--green-dark); font-size: 11px; font-weight: 700; text-decoration-thickness: 1px; text-underline-offset: 3px; }
.empty-state, .error-state, .loading-state { padding: 36px 15px; color: var(--muted); text-align: center; font-size: 12px; }
.error-state { color: #a34432; }
.error-state p { margin: 0 0 12px; }
.retry-button { min-height: 36px; padding: 0 13px; border: 1px solid var(--green); border-radius: 3px; color: var(--green-dark); background: white; font-size: 11px; font-weight: 800; cursor: pointer; }
.retry-button:hover { color: white; background: var(--green-dark); }
.loading-state { display: flex; justify-content: center; align-items: center; gap: 10px; }
.loader { width: 16px; aspect-ratio: 1; border: 2px solid var(--line); border-top-color: var(--green); border-radius: 50%; animation: spin .8s linear infinite; }
.footer { max-width: 1180px; margin: 0 auto; padding: 25px 34px 32px; display: flex; justify-content: space-between; gap: 16px; color: var(--muted); font-size: 10px; }
.footer-separator { padding: 0 6px; color: var(--coral); }

@keyframes rise-in { from { opacity: 0; transform: translateY(9px); } to { opacity: 1; transform: translateY(0); } }
@keyframes spin { to { transform: rotate(360deg); } }

@media (max-width: 720px) {
  .topbar { min-height: 62px; padding: 0 18px; }
  .topbar-meta { display: none; }
  main { padding: 0 16px; }
  .intro { min-height: 0; padding: 42px 0 34px; }
  .intro::after { width: 90px; height: 90px; right: 12px; top: 27px; }
  .intro-note { display: none; }
  h1 { max-width: 560px; font-size: 39px; }
  .intro-text { max-width: 420px; font-size: 13px; }
  .contact-button { margin-top: 18px; }
  .library { padding: 23px 16px 27px; }
  .library-heading { align-items: center; }
  h2 { font-size: 19px; }
  .level-list { grid-template-columns: 1fr; gap: 8px; }
  .level-item { min-height: 70px; }
  .breadcrumbs { gap: 6px; overflow-x: auto; white-space: nowrap; }
  .exercise-body { padding: 5px 14px 16px; }
  .footer { padding: 22px 18px 27px; flex-direction: column; gap: 6px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; scroll-behavior: auto !important; transition-duration: .01ms !important; }
}