.u4-investigation{margin:2rem auto;padding:clamp(1rem,2vw,1.5rem);max-width:76rem;border:2px solid var(--border-strong,#597386);border-radius:1.25rem;background:var(--surface,#fff);color:var(--ink,#122b3a);box-shadow:0 12px 36px #142f4314}
.u4-investigation *{box-sizing:border-box}
.u4-investigation-heading{display:flex;justify-content:space-between;align-items:start;gap:1rem;flex-wrap:wrap}
.u4-investigation h2{margin:.2rem 0 .8rem;font-size:clamp(1.35rem,2.2vw,1.8rem)}
.u4-investigation h3{font-size:1.2rem;margin:.2rem 0 .5rem}
.u4-investigation-kicker{margin:0;color:var(--brand,#126a75);font-weight:800;letter-spacing:.07em;text-transform:uppercase;font-size:.8rem}
.u4-investigation-evidence{margin:0;padding:.35rem .7rem;border-radius:2rem;border:1px solid var(--border,#aec1c8);font-weight:700;font-size:.9rem}
.u4-entry{margin:1rem 0;padding:1rem;border:1px solid var(--border,#aec1c8);border-radius:.75rem}
.u4-entry summary{cursor:pointer;font-weight:800;min-height:2.75rem}
.u4-entry-items{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,15rem),1fr));gap:.8rem}
.u4-investigation-workspace{display:grid;grid-template-columns:minmax(15rem,1fr) minmax(0,1.5fr);gap:1rem;align-items:start}
.u4-investigation-controls{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:.7rem}
.u4-investigation label,.u4-entry label{display:grid;gap:.35rem;font-weight:700;min-width:0}
.u4-investigation input,.u4-investigation textarea{width:100%;min-height:3rem;padding:.65rem .75rem;border:2px solid var(--border-strong,#597386);border-radius:.6rem;background:var(--surface,#fff);color:var(--ink,#122b3a);font:inherit;font-size:1rem}
.u4-investigation textarea{resize:vertical}
.u4-investigation :is(input,textarea,button,summary):focus-visible{outline:3px solid #f59b2e;outline-offset:3px}
.u4-investigation-model{padding:1rem;border-radius:.8rem;background:var(--surface-2,#edf6f7);border:1px solid var(--border,#aec1c8)}
.u4-investigation-bar{display:grid;grid-template-columns:minmax(5rem,1fr) minmax(0,5fr) 3.5rem;align-items:center;gap:.6rem;margin:.4rem 0}
.u4-investigation-track{height:2.25rem;border-radius:.45rem;border:2px solid var(--brand,#126a75);background:repeating-linear-gradient(90deg,transparent 0 calc(10% - 1px),#526873 10%)}
.u4-investigation-track span{display:block;height:100%;background:#2aa79c;transition:width .2s ease}
.u4-investigation-equation{overflow-wrap:anywhere;font-size:1.1rem;font-weight:800}
.u4-investigation-label{margin:1rem 0}
.u4-investigation button{min-height:3rem;margin:.3rem .5rem .3rem 0;padding:.6rem 1rem}
.u4-test-result,.u4-independent-feedback,.u4-entry-result{min-height:1.7rem;line-height:1.5}
.u4-independent{margin-top:1.2rem;padding:1rem;border:2px solid var(--brand,#126a75);border-radius:.85rem}
@media(max-width:700px){.u4-investigation-workspace{grid-template-columns:1fr}.u4-investigation-controls{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media(max-width:380px){.u4-investigation-controls{grid-template-columns:1fr}}
@media(prefers-reduced-motion:reduce){.u4-investigation-track span{transition:none}}
@media(forced-colors:active){.u4-investigation,.u4-independent,.u4-investigation-track{border-color:CanvasText}.u4-investigation-track span{background:Highlight}}