/* House design system — S4S family
   Two-tone: deep navy + amber accent. Serif headlines, small-caps labels,
   hairline dividers. No emoji, no decorative graphics. */

:root {
  --navy: #0f172a;
  --navy-2: #16213c;
  --navy-3: #1e2b49;
  --amber: #f59e0b;
  --amber-soft: #fcd34d;
  --ink: #e8ecf4;
  --ink-dim: #97a3bb;
  --ink-faint: #6b7893;
  --line: rgba(255, 255, 255, 0.09);
  --line-2: rgba(255, 255, 255, 0.16);
  --good: #34d399;
  --bad: #f87171;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  --radius: 10px;
  --maxw: 1080px;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-padding-top: 80px; scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--navy);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

/* ---------- header ---------- */
.app-header {
  border-bottom: 1px solid var(--line);
  background: rgba(15, 23, 42, 0.92);
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(8px);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  min-height: 62px;
  flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 10px; }
.brand-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px; height: 32px;
  border-radius: 8px;
  background: var(--amber);
  color: var(--navy);
  flex: none;
}
.brand-text {
  font-family: var(--serif);
  font-size: 1.06rem;
  letter-spacing: 0.01em;
  color: #fff;
}
.header-nav { display: flex; gap: 4px; }
.nav-link {
  color: var(--ink-dim);
  text-decoration: none;
  font-size: 0.84rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 7px 12px;
  border-radius: 7px;
  transition: color .15s, background .15s;
}
.nav-link:hover { color: var(--ink); background: rgba(255,255,255,.05); }
.nav-link.is-active { color: var(--amber); }

/* ---------- hero ---------- */
.hero { padding: 60px 0 34px; max-width: 760px; }
.eyebrow {
  font-size: 0.72rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--amber);
  margin: 0 0 14px;
}
.hero h1 {
  font-family: var(--serif);
  font-size: clamp(1.85rem, 4.4vw, 2.85rem);
  line-height: 1.16;
  font-weight: 500;
  margin: 0 0 18px;
  color: #fff;
  letter-spacing: -0.01em;
}
.lede { color: var(--ink-dim); font-size: 1.03rem; margin: 0; max-width: 66ch; }

/* ---------- stats ---------- */
.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  margin: 34px 0 30px;
}
.stat { background: var(--navy-2); padding: 20px 18px; }
.stat-value {
  display: block;
  font-family: var(--serif);
  font-size: 1.85rem;
  line-height: 1;
  color: #fff;
}
.stat-label {
  display: block;
  font-size: 0.7rem;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin-top: 9px;
}

/* ---------- search + filters ---------- */
.searchbar-wrap { margin-bottom: 30px; }
.searchbar {
  width: 100%;
  padding: 13px 15px;
  font-size: 0.95rem;
  font-family: inherit;
  color: var(--ink);
  background: var(--navy-2);
  border: 1px solid var(--line-2);
  border-radius: var(--radius);
  outline: none;
  transition: border-color .15s;
}
.searchbar::placeholder { color: var(--ink-faint); }
.searchbar:focus { border-color: var(--amber); }

.filters { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.tab-btn {
  font-family: inherit;
  font-size: 0.82rem;
  color: var(--ink-dim);
  background: transparent;
  border: 1px solid var(--line-2);
  border-radius: 999px;
  padding: 6px 14px;
  cursor: pointer;
  transition: all .15s;
}
.tab-btn:hover { color: var(--ink); border-color: var(--ink-faint); }
.tab-btn.is-active {
  color: var(--navy);
  background: var(--amber);
  border-color: var(--amber);
  font-weight: 600;
}
.tab-count { opacity: .65; font-size: 0.78em; margin-left: 3px; }
.tab-btn.is-active .tab-count { opacity: .7; }

/* ---------- cert block ---------- */
.cert-block {
  border-top: 1px solid var(--line);
  padding: 28px 0 8px;
  margin-bottom: 26px;
}
.cert-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 18px;
  flex-wrap: wrap;
  margin-bottom: 18px;
}
.cert-name {
  font-family: var(--serif);
  font-size: 1.35rem;
  font-weight: 500;
  margin: 0;
  color: #fff;
}
.cert-meta {
  margin: 5px 0 0;
  font-size: 0.72rem;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.cert-actions { display: flex; gap: 8px; flex: none; }

.btn {
  font-family: inherit;
  font-size: 0.82rem;
  color: var(--navy);
  background: var(--amber);
  border: 1px solid var(--amber);
  border-radius: 7px;
  padding: 8px 15px;
  cursor: pointer;
  text-decoration: none;
  display: inline-block;
  transition: filter .15s;
}
.btn:hover { filter: brightness(1.08); }
.btn-ghost {
  color: var(--ink-dim);
  background: transparent;
  border-color: var(--line-2);
}
.btn-ghost:hover { color: var(--ink); border-color: var(--ink-faint); filter: none; }

/* ---------- question card ---------- */
.q-card {
  background: var(--navy-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px 22px;
  margin-bottom: 14px;
}
.q-head { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; margin-bottom: 11px; }
.q-num {
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--navy);
  background: var(--amber);
  border-radius: 4px;
  padding: 2px 7px;
  font-weight: 700;
}
.q-tag {
  font-size: 0.68rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  border: 1px solid var(--line-2);
  border-radius: 999px;
  padding: 2px 9px;
}
.q-tag-alt { color: var(--amber-soft); border-color: rgba(245,158,11,.3); }
.q-text {
  font-family: var(--serif);
  font-size: 1.08rem;
  font-weight: 500;
  line-height: 1.45;
  margin: 0 0 15px;
  color: #fff;
}

.opts { display: flex; flex-direction: column; gap: 7px; }
.opt {
  display: flex;
  align-items: flex-start;
  gap: 11px;
  padding: 10px 13px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255,255,255,.015);
  font-size: 0.94rem;
  transition: border-color .15s, background .15s;
}
.opt-letter {
  font-family: var(--mono);
  font-size: 0.8rem;
  color: var(--ink-faint);
  flex: none;
  width: 16px;
  padding-top: 1px;
}
.opt-text { flex: 1; }
.opt input[type="radio"] { margin: 3px 0 0; accent-color: var(--amber); flex: none; }
.opt:has(input:checked) { border-color: var(--amber); background: rgba(245,158,11,.07); }
.opt.is-key { border-color: rgba(52,211,153,.45); background: rgba(52,211,153,.08); }
.opt.is-key .opt-letter { color: var(--good); }
.opt.is-wrong { border-color: rgba(248,113,113,.45); background: rgba(248,113,113,.08); }
.opt.is-wrong .opt-letter { color: var(--bad); }
.opt.is-revealed { cursor: default; }
.opt-badge {
  font-size: 0.66rem;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--good);
  border: 1px solid rgba(52,211,153,.4);
  border-radius: 999px;
  padding: 1px 8px;
  flex: none;
  align-self: center;
}
.opt-flag {
  font-size: 0.66rem;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  flex: none;
  align-self: center;
  color: var(--ink-faint);
}

.q-answer {
  display: flex;
  align-items: baseline;
  gap: 9px;
  flex-wrap: wrap;
  margin-top: 15px;
  padding-top: 13px;
  border-top: 1px solid var(--line);
  font-size: 0.9rem;
}
.ans-label, .expl-label {
  font-size: 0.66rem;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.q-answer strong { color: var(--amber); font-family: var(--mono); font-size: 0.92rem; }
.q-answer span:last-child { color: var(--ink-dim); }

.q-expl { margin-top: 13px; }
.q-expl p { margin: 5px 0 0; font-size: 0.92rem; color: var(--ink-dim); }

/* ---------- drill ---------- */
.drill-foot { display: flex; gap: 9px; margin-top: 16px; }

/* ---------- panel ---------- */
.panel {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--navy-2);
  padding: 26px 28px;
  margin: 40px 0 60px;
}
.panel-title {
  font-family: var(--serif);
  font-size: 1.3rem;
  font-weight: 500;
  margin: 0 0 14px;
  color: #fff;
}
.panel-body { color: var(--ink-dim); margin: 0 0 13px; font-size: 0.95rem; max-width: 74ch; }
.panel-body:last-child { margin-bottom: 0; }
.panel-body code {
  font-family: var(--mono);
  font-size: 0.85em;
  background: rgba(255,255,255,.06);
  padding: 1px 5px;
  border-radius: 4px;
}
.panel-body a { color: var(--amber); }

/* ---------- empty ---------- */
.empty {
  text-align: center;
  padding: 60px 20px;
  border: 1px dashed var(--line-2);
  border-radius: var(--radius);
  color: var(--ink-dim);
}
.empty h3 { font-family: var(--serif); color: #fff; margin: 0 0 8px; }
.empty-sub { color: var(--ink-faint); font-size: 0.9rem; margin: 0; }

/* ---------- footer ---------- */
.app-footer {
  border-top: 1px solid var(--line);
  padding: 24px 0 40px;
  color: var(--ink-faint);
  font-size: 0.82rem;
}
.app-footer p { margin: 0; }

/* ---------- responsive ---------- */
@media (max-width: 760px) {
  .wrap { padding: 0 16px; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .hero { padding: 38px 0 26px; }
  .q-card { padding: 16px 15px; }
  .cert-head { flex-direction: column; align-items: stretch; }
  .cert-actions { flex-wrap: wrap; }
  .header-inner { min-height: 56px; }
  .nav-link { padding: 6px 9px; font-size: 0.78rem; }
  .panel { padding: 20px 17px; }
  .stat { padding: 15px 13px; }
  .stat-value { font-size: 1.5rem; }
}