/* ===== EconAcademy — IGCSE Economics ===== */
:root {
  --bg: #f7f9f9;
  --surface: #ffffff;
  --ink: #21242c;
  --ink-soft: #5b6472;
  --line: #e3e8ee;
  --brand: #14a45c;       /* khan-ish green */
  --brand-dark: #0f7d46;
  --brand-soft: #e7f6ee;
  --accent: #1865f2;      /* learn blue */
  --accent-soft: #e8f0fe;
  --warn: #d97706;
  --danger: #d23f3f;
  --danger-soft: #fdeaea;
  --ok: #14a45c;
  --ok-soft: #e7f6ee;
  --shadow: 0 1px 2px rgba(16,24,40,.05), 0 4px 16px rgba(16,24,40,.06);
  --radius: 14px;
  --sidebar-w: 312px;
  --maxread: 760px;
  font-synthesis: none;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ===== Topbar ===== */
.topbar {
  position: sticky; top: 0; z-index: 40;
  height: 60px; display: flex; align-items: center; gap: 14px;
  padding: 0 18px;
  background: var(--surface);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 9px; color: var(--ink); font-size: 20px; }
.brand:hover { text-decoration: none; }
.brand-mark { font-size: 22px; }
.brand-name { font-weight: 500; letter-spacing: -.2px; }
.brand-name strong { color: var(--brand-dark); font-weight: 800; }
.topbar-right { margin-left: auto; display: flex; align-items: center; gap: 16px; }
.overall-progress { display: flex; align-items: center; gap: 9px; }
.op-bar { width: 120px; height: 9px; background: var(--line); border-radius: 99px; overflow: hidden; }
.op-fill { height: 100%; width: 0; background: linear-gradient(90deg, var(--brand), var(--brand-dark)); border-radius: 99px; transition: width .5s ease; }
.op-label { font-size: 13px; font-weight: 700; color: var(--ink-soft); min-width: 34px; }
.menu-toggle { display: none; background: none; border: 0; font-size: 22px; cursor: pointer; color: var(--ink); padding: 4px 6px; }

/* ===== Layout ===== */
.layout { display: flex; align-items: flex-start; }
.sidebar {
  position: sticky; top: 60px;
  width: var(--sidebar-w); flex: 0 0 var(--sidebar-w);
  height: calc(100vh - 60px); overflow-y: auto;
  background: var(--surface); border-right: 1px solid var(--line);
}
.sidebar-inner { padding: 16px 12px 60px; }
.main { flex: 1 1 auto; min-width: 0; padding: 30px clamp(18px, 5vw, 56px) 90px; }
.scrim { display: none; }

/* ===== Sidebar nav ===== */
.nav-section { margin-bottom: 18px; }
.nav-section-title {
  font-size: 11px; font-weight: 800; letter-spacing: .8px; text-transform: uppercase;
  color: var(--ink-soft); padding: 6px 12px; margin: 4px 0;
}
.nav-chapter {
  display: flex; align-items: center; gap: 11px;
  padding: 9px 12px; border-radius: 10px; cursor: pointer;
  color: var(--ink); font-size: 14.5px; transition: background .12s;
}
.nav-chapter:hover { background: var(--bg); text-decoration: none; }
.nav-chapter.active { background: var(--brand-soft); color: var(--brand-dark); font-weight: 700; }
.nav-num {
  flex: 0 0 26px; height: 26px; border-radius: 8px;
  display: grid; place-items: center; font-size: 12px; font-weight: 800;
  background: var(--bg); color: var(--ink-soft); border: 1px solid var(--line);
}
.nav-chapter.active .nav-num { background: var(--brand); color: #fff; border-color: var(--brand); }
.nav-chapter.done .nav-num { background: var(--brand); color: #fff; border-color: var(--brand); }
.nav-title { flex: 1; line-height: 1.3; }
.nav-check { font-size: 14px; color: var(--brand); }

/* ===== Home ===== */
.hero {
  background: linear-gradient(135deg, #0f7d46, #14a45c 60%, #1bbf6b);
  color: #fff; border-radius: 20px; padding: 38px 36px;
  margin-bottom: 30px; box-shadow: var(--shadow);
}
.hero h1 { margin: 0 0 8px; font-size: clamp(26px, 4vw, 36px); letter-spacing: -.5px; }
.hero p { margin: 0; font-size: 16px; max-width: 640px; opacity: .95; }
.hero .hero-meta { margin-top: 18px; display: flex; gap: 22px; flex-wrap: wrap; font-size: 14px; }
.hero .hero-meta b { font-size: 22px; display: block; }

.section-block { margin-bottom: 34px; }
.section-block > h2 {
  font-size: 14px; text-transform: uppercase; letter-spacing: .6px;
  color: var(--ink-soft); margin: 0 0 14px; font-weight: 800;
}
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 16px; }
.ch-card {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 18px 18px 16px; cursor: pointer; transition: transform .12s, box-shadow .12s, border-color .12s;
  display: flex; flex-direction: column; gap: 10px; position: relative; overflow: hidden;
}
.ch-card:hover { transform: translateY(-2px); box-shadow: var(--shadow); border-color: #cfe9da; text-decoration: none; }
.ch-card .ch-top { display: flex; align-items: center; gap: 12px; }
.ch-badge {
  flex: 0 0 42px; height: 42px; border-radius: 11px; display: grid; place-items: center;
  font-weight: 800; font-size: 16px; background: var(--brand-soft); color: var(--brand-dark);
}
.ch-card h3 { margin: 0; font-size: 16.5px; line-height: 1.25; color: var(--ink); }
.ch-card .ch-sub { font-size: 13px; color: var(--ink-soft); }
.ch-card .ch-foot { display: flex; align-items: center; justify-content: space-between; margin-top: 4px; }
.ch-prog { flex: 1; height: 7px; background: var(--bg); border-radius: 99px; overflow: hidden; margin-right: 10px; }
.ch-prog > i { display: block; height: 100%; background: var(--brand); border-radius: 99px; }
.ch-stat { font-size: 12px; font-weight: 700; color: var(--ink-soft); }
.ch-card .pill { position: absolute; top: 14px; right: 14px; font-size: 11px; font-weight: 800; padding: 3px 9px; border-radius: 99px; }
.pill.mastered { background: var(--brand); color: #fff; }

/* ===== Chapter view ===== */
.breadcrumb { font-size: 13px; color: var(--ink-soft); margin-bottom: 14px; }
.chapter-head { max-width: var(--maxread); margin-bottom: 26px; }
.chapter-head .eyebrow { color: var(--brand-dark); font-weight: 800; font-size: 13px; letter-spacing: .4px; text-transform: uppercase; }
.chapter-head h1 { font-size: clamp(24px, 4vw, 34px); margin: 6px 0 14px; letter-spacing: -.5px; }
.objectives { background: var(--accent-soft); border: 1px solid #d6e4fd; border-radius: var(--radius); padding: 16px 18px; }
.objectives h4 { margin: 0 0 8px; font-size: 13px; text-transform: uppercase; letter-spacing: .4px; color: var(--accent); }
.objectives ul { margin: 0; padding-left: 20px; }
.objectives li { margin: 3px 0; }

.lesson {
  max-width: var(--maxread); background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 22px 26px; margin-bottom: 16px; scroll-margin-top: 76px;
}
.lesson > .lesson-id { font-size: 12px; font-weight: 800; color: var(--brand-dark); letter-spacing: .5px; }
.lesson > h2 { font-size: 21px; margin: 4px 0 14px; letter-spacing: -.3px; }
.lesson-body { font-size: 16px; color: #2b303a; }
.lesson-body p { margin: 0 0 14px; }
.lesson-body h4 { font-size: 16px; margin: 20px 0 8px; color: var(--ink); }
.lesson-body ul, .lesson-body ol { margin: 0 0 14px; padding-left: 22px; }
.lesson-body li { margin: 5px 0; }
.lesson-body strong { color: var(--ink); }
.lesson-body table { width: 100%; border-collapse: collapse; margin: 6px 0 16px; font-size: 14.5px; }
.lesson-body th, .lesson-body td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; }
.lesson-body th { background: var(--bg); font-weight: 700; }

.keyterms { margin-top: 16px; display: grid; gap: 10px; }
.keyterm { background: var(--brand-soft); border-left: 4px solid var(--brand); border-radius: 8px; padding: 10px 14px; font-size: 14.5px; }
.keyterm b { color: var(--brand-dark); }
.tipbox { margin-top: 14px; background: #fff7ea; border-left: 4px solid var(--warn); border-radius: 8px; padding: 10px 14px; font-size: 14.5px; }
.tipbox b { color: var(--warn); }

.summary {
  max-width: var(--maxread); background: linear-gradient(180deg, #fff, #f5fbf7);
  border: 1px solid #cdeada; border-radius: var(--radius); padding: 20px 24px; margin: 22px 0;
}
.summary h3 { margin: 0 0 10px; font-size: 17px; color: var(--brand-dark); }
.summary ul { margin: 0; padding-left: 22px; }
.summary li { margin: 6px 0; }

/* ===== Buttons ===== */
.btn {
  display: inline-flex; align-items: center; gap: 8px; cursor: pointer;
  border: 0; border-radius: 11px; font-weight: 700; font-size: 15px; padding: 12px 22px;
  background: var(--brand); color: #fff; transition: background .12s, transform .06s;
}
.btn:hover { background: var(--brand-dark); text-decoration: none; }
.btn:active { transform: translateY(1px); }
.btn.secondary { background: var(--surface); color: var(--ink); border: 1px solid var(--line); }
.btn.secondary:hover { background: var(--bg); }
.btn.big { font-size: 16px; padding: 14px 26px; }
.btn[disabled] { opacity: .5; cursor: not-allowed; }
.btn-row { display: flex; gap: 12px; flex-wrap: wrap; align-items: center; margin-top: 8px; }

.quiz-cta {
  max-width: var(--maxread); background: var(--surface); border: 2px dashed #bfe3cf;
  border-radius: var(--radius); padding: 24px; margin: 24px 0; text-align: center;
}
.quiz-cta h3 { margin: 0 0 6px; font-size: 20px; }
.quiz-cta p { margin: 0 0 16px; color: var(--ink-soft); }

/* ===== Quiz ===== */
.quiz-wrap { max-width: var(--maxread); }
.quiz-progress { display: flex; align-items: center; gap: 12px; margin-bottom: 18px; }
.quiz-progress .qp-bar { flex: 1; height: 9px; background: var(--line); border-radius: 99px; overflow: hidden; }
.quiz-progress .qp-fill { height: 100%; background: var(--accent); border-radius: 99px; transition: width .3s; }
.quiz-progress .qp-count { font-size: 13px; font-weight: 700; color: var(--ink-soft); }
.qcard { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 26px; box-shadow: var(--shadow); }
.qcard .qnum { font-size: 12px; font-weight: 800; color: var(--accent); letter-spacing: .5px; text-transform: uppercase; }
.qcard .qtext { font-size: 19px; font-weight: 600; margin: 8px 0 20px; line-height: 1.4; }
.options { display: grid; gap: 11px; }
.option {
  display: flex; align-items: flex-start; gap: 12px; padding: 14px 16px;
  border: 1.5px solid var(--line); border-radius: 12px; cursor: pointer; background: var(--surface);
  transition: border-color .12s, background .12s; font-size: 15.5px;
}
.option:hover { border-color: var(--accent); background: var(--accent-soft); }
.option .opt-key { flex: 0 0 26px; height: 26px; border-radius: 7px; display: grid; place-items: center; font-weight: 800; font-size: 13px; background: var(--bg); color: var(--ink-soft); border: 1px solid var(--line); }
.option.selected { border-color: var(--accent); background: var(--accent-soft); }
.option.selected .opt-key { background: var(--accent); color: #fff; border-color: var(--accent); }
.option.correct { border-color: var(--ok); background: var(--ok-soft); }
.option.correct .opt-key { background: var(--ok); color: #fff; border-color: var(--ok); }
.option.wrong { border-color: var(--danger); background: var(--danger-soft); }
.option.wrong .opt-key { background: var(--danger); color: #fff; border-color: var(--danger); }
.option.locked { cursor: default; pointer-events: none; }
.option.dim { opacity: .55; }

.feedback { margin-top: 18px; border-radius: 12px; padding: 14px 16px; font-size: 15px; display: none; }
.feedback.show { display: block; }
.feedback.good { background: var(--ok-soft); border: 1px solid #bfe3cf; }
.feedback.bad { background: var(--danger-soft); border: 1px solid #f3cccc; }
.feedback .fb-title { font-weight: 800; margin-bottom: 4px; }
.feedback.good .fb-title { color: var(--brand-dark); }
.feedback.bad .fb-title { color: var(--danger); }

/* ===== Results ===== */
.results { max-width: var(--maxread); text-align: center; background: var(--surface); border: 1px solid var(--line); border-radius: 20px; padding: 40px 30px; box-shadow: var(--shadow); }
.score-ring { width: 150px; height: 150px; margin: 0 auto 18px; position: relative; }
.score-ring svg { transform: rotate(-90deg); }
.score-ring .ring-num { position: absolute; inset: 0; display: grid; place-items: center; font-size: 34px; font-weight: 800; }
.results h2 { margin: 0 0 6px; font-size: 26px; }
.results .res-sub { color: var(--ink-soft); margin-bottom: 22px; }
.review-list { text-align: left; margin-top: 26px; display: grid; gap: 12px; }
.review-item { border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; }
.review-item .ri-q { font-weight: 600; margin-bottom: 8px; }
.review-item .ri-line { font-size: 14px; margin: 2px 0; }
.ri-line.you-wrong { color: var(--danger); }
.ri-line.you-right { color: var(--brand-dark); }
.ri-line .lbl { font-weight: 700; }
.review-item .ri-exp { font-size: 14px; color: var(--ink-soft); margin-top: 8px; padding-top: 8px; border-top: 1px dashed var(--line); }

.empty { max-width: var(--maxread); padding: 40px; text-align: center; color: var(--ink-soft); }
.loading { padding: 60px; text-align: center; color: var(--ink-soft); }
.spinner { width: 30px; height: 30px; border: 3px solid var(--line); border-top-color: var(--brand); border-radius: 50%; margin: 0 auto 14px; animation: spin 1s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

footer.page-foot { max-width: var(--maxread); margin-top: 40px; font-size: 12.5px; color: var(--ink-soft); border-top: 1px solid var(--line); padding-top: 16px; }

/* ===== Responsive ===== */
@media (max-width: 880px) {
  .menu-toggle { display: block; }
  .sidebar {
    position: fixed; top: 60px; left: 0; z-index: 35;
    transform: translateX(-100%); transition: transform .25s ease; box-shadow: var(--shadow);
  }
  .sidebar.open { transform: translateX(0); }
  .scrim.show { display: block; position: fixed; inset: 60px 0 0 0; background: rgba(0,0,0,.35); z-index: 30; }
  .overall-progress .op-bar { width: 80px; }
}