/* Cube Folding drill (cube-folding-test.html) */
.cf-wrap { max-width: 860px; margin: 64px auto 56px; padding: 0 18px; }
.cf-card { background: var(--bg-card, #fff); border: 1px solid var(--border-color, #e5e7eb); border-radius: 18px; padding: 24px 24px 22px;
  box-shadow: 0 8px 28px rgba(17, 24, 39, .07); margin-bottom: 16px; }
.cf-kicker { font-size: 11.5px; letter-spacing: .08em; text-transform: uppercase; font-weight: 800; color: var(--accent, #4c8bf5); }
.cf-title { font-size: clamp(1.6rem, 3vw, 2.1rem); font-weight: 800; letter-spacing: -.01em; margin: 6px 0 8px; color: var(--text-bright, #111827); }
.cf-lede { font-size: 15.5px; line-height: 1.6; color: var(--text-secondary, #4b5563); margin: 0 0 18px; max-width: 66ch; }
.cf-pick { margin: 0 0 14px; }
.cf-pick__lbl { font-size: 12px; font-weight: 800; letter-spacing: .06em; text-transform: uppercase; color: var(--text-muted, #9ca3af); margin-bottom: 6px; }
.cf-seg { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 8px; }
.cf-seg--len { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.cf-seg__b { text-align: left; border: 1.5px solid var(--border-color, #e5e7eb); background: var(--bg-darker, #f6f7f9); border-radius: 12px; padding: 10px 12px; cursor: pointer;
  display: flex; flex-direction: column; gap: 3px; color: var(--text-primary, #111827); font: inherit; }
.cf-seg--len .cf-seg__b { text-align: center; align-items: center; }
.cf-seg__b b { font-size: 15px; }
.cf-seg__b span { font-size: 12.5px; line-height: 1.4; color: var(--text-secondary, #6b7280); }
.cf-seg__b.is-on { border-color: var(--accent, #4c8bf5); background: color-mix(in srgb, var(--accent, #4c8bf5) 8%, var(--bg-card, #fff)); }
.cf-seg__b.is-locked { opacity: .78; }
.cf-pro { display: inline-block; font-size: 10.5px; font-weight: 800; letter-spacing: .06em; text-transform: uppercase; padding: 2px 7px; border-radius: 999px;
  background: rgba(76, 95, 213, .12); color: #4c5fd5; vertical-align: 2px; }
.cf-landing__go { display: flex; align-items: center; gap: 14px; flex-wrap: wrap; margin-top: 18px; }
.cf-start { min-height: 46px; padding: 0 22px; font-size: 15px; }
.cf-best { font-size: 14px; color: var(--text-secondary, #6b7280); }
.cf-note { font-size: 13.5px; color: var(--text-secondary, #6b7280); margin: 14px 0 0; }
.cf-note a { color: var(--accent, #4c8bf5); font-weight: 600; }

.cf-hud { display: flex; align-items: center; gap: 18px; padding-bottom: 12px; border-bottom: 1px solid var(--border-color, #eef0f3); margin-bottom: 12px; }
.cf-hud__item { display: flex; flex-direction: column; }
.cf-hud__item span { font-size: 11px; font-weight: 800; letter-spacing: .07em; text-transform: uppercase; color: var(--text-muted, #9ca3af); }
.cf-hud__item b { font: 800 22px/1.1 'JetBrains Mono', ui-monospace, monospace; color: var(--text-bright, #111827); font-variant-numeric: tabular-nums; }
.cf-clock.is-low { color: #dc2626; }
.cf-quit { margin-left: auto; border: 1px solid var(--border-color, #e5e7eb); background: none; border-radius: 10px; padding: 7px 14px; font-weight: 700; cursor: pointer; color: var(--text-secondary, #6b7280); }
.cf-q { font-size: 17px; font-weight: 700; color: var(--text-bright, #111827); margin: 4px 0 10px; text-align: center; }
.cf-net { max-width: 300px; margin: 0 auto 14px; }
.cf-net svg { display: block; width: 100%; height: auto; }
.cf-opts { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 10px; }
.cf-opt { position: relative; border: 1.5px solid var(--border-color, #e5e7eb); background: var(--bg-darker, #f6f7f9); border-radius: 13px; padding: 22px 6px 8px; cursor: pointer;
  transition: transform .1s ease, border-color .15s ease; }
.cf-opt:hover { transform: translateY(-2px); border-color: var(--accent, #4c8bf5); background: var(--bg-card, #fff); }
.cf-opt svg { display: block; width: 100%; height: auto; max-width: 130px; margin: 0 auto; }
.cf-opt__k { position: absolute; top: 6px; left: 8px; font-size: 12px; font-weight: 800; color: var(--text-muted, #9ca3af); }
.cf-opt.is-ok { border: 2.5px solid #16a34a; background: rgba(22, 163, 74, .08); }
.cf-opt.is-no { border: 2.5px solid #dc2626; background: rgba(220, 38, 38, .07); }
.cf-keys { font-size: 12px; color: var(--text-muted, #9ca3af); text-align: center; margin: 10px 0 0; }

.cf-done { text-align: center; }
.cf-done__score { display: flex; flex-direction: column; align-items: center; margin: 8px 0 12px; }
.cf-done__score b { font-size: 3rem; font-weight: 800; line-height: 1; color: var(--text-bright, #111827); }
.cf-done__score span { font-size: 13px; color: var(--text-secondary, #6b7280); margin-top: 4px; }
.cf-done__stats { display: flex; justify-content: center; gap: 10px; flex-wrap: wrap; }
.cf-done__stats > div { min-width: 76px; padding: 8px 12px; border: 1px solid var(--border-color, #e5e7eb); border-radius: 12px; display: flex; flex-direction: column; }
.cf-done__stats b { font-size: 1.2rem; color: var(--text-bright, #111827); }
.cf-done__stats span { font-size: 12px; color: var(--text-secondary, #6b7280); }
.cf-done__best { font-size: 14px; font-weight: 600; color: var(--text-secondary, #4b5563); margin: 12px 0 0; }
.cf-done__cta { display: flex; justify-content: center; gap: 10px; flex-wrap: wrap; margin-top: 16px; }
.cf-rev-h { font-size: 1.15rem; margin: 22px 4px 10px; color: var(--text-bright, #111827); }
.cf-rev-h--ok { text-align: center; color: #16a34a; }
.cf-rev__head { font-weight: 700; font-size: 14.5px; margin-bottom: 8px; color: var(--text-bright, #111827); }
.cf-rev__net { max-width: 230px; margin: 0 auto 10px; }
.cf-rev__net svg { width: 100%; height: auto; display: block; }
.cf-rev__opts { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 8px; }
.cf-rev__o { position: relative; border: 1px solid var(--border-color, #e5e7eb); border-radius: 10px; padding: 16px 4px 4px; }
.cf-rev__o > span { position: absolute; top: 3px; left: 7px; font-size: 11px; font-weight: 800; color: var(--text-muted, #9ca3af); }
.cf-rev__o svg { width: 100%; height: auto; display: block; max-width: 110px; margin: 0 auto; }
.cf-rev__o.is-key { border: 2px solid #16a34a; }
.cf-rev__o.is-pick { border: 2px solid #dc2626; }
.cf-rev__ex { font-size: 14px; line-height: 1.6; color: var(--text-secondary, #4b5563); margin: 10px 0 0; }

.cf-article { max-width: 760px; margin: 30px auto 0; font-size: 15.5px; line-height: 1.7; color: var(--text-primary, #1f2937); }
.cf-article h2 { font-size: 1.3rem; margin: 28px 0 8px; color: var(--text-bright, #111827); }
.cf-article h3 { font-size: 1.05rem; margin: 18px 0 4px; color: var(--text-bright, #111827); }
.cf-article p, .cf-article li { color: var(--text-secondary, #374151); }
.cf-article a { color: var(--accent, #4c8bf5); font-weight: 600; text-decoration: none; }

@media (max-width: 640px) {
  .cf-wrap { margin-top: 56px; padding: 0 12px; }
  .cf-card { padding: 16px 14px; }
  .cf-seg { grid-template-columns: 1fr; }
  .cf-seg--len { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .cf-opts, .cf-rev__opts { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .cf-hud { gap: 12px; }
  .cf-hud__item b { font-size: 19px; }
  .cf-net { max-width: 240px; }
}
@media (max-width: 640px) {
  .cf-seg__b span { font-size: 12px; }
  .cf-seg--len .cf-seg__b { padding: 10px 4px; white-space: nowrap; }
  .cf-seg--len .cf-seg__b b { font-size: 14px; }
  .cf-start { width: 100%; }
}
/* focus mode during a run: no site nav, no sample badge (the Easy drill is fully free) */
body.cf-running > nav.nav, body.cf-running .cf-article, body.cf-running #qv-sample-badge { display: none !important; }
body.cf-running .cf-wrap { margin-top: 16px; }
#qv-sample-badge { display: none !important; }
.cf-rev > summary { cursor: pointer; list-style: none; display: flex; justify-content: space-between; gap: 10px; }
.cf-rev > summary::-webkit-details-marker { display: none; }
.cf-rev__t { font-weight: 600; color: var(--text-muted, #9ca3af); font-size: 13px; }
.cf-rev--ok .cf-rev__head { color: #166534; }
@media (hover: none) { .cf-keys { display: none; } }
.cf-net svg { max-height: 240px; width: auto; max-width: 100%; margin: 0 auto; }
@media (max-width: 640px) { .cf-net svg { max-height: 200px; } }