.flash-main{max-width:1200px}.flash-intro{margin-bottom:24px}.flash-intro h1{font-size:clamp(1.8rem,4vw,2.8rem);margin:5px 0}.flash-intro .lead{font-size:1rem}.flash-tools{display:flex;align-items:end;gap:14px;flex-wrap:wrap;margin:20px 0}.flash-tools label{font-size:.85rem;font-weight:600;display:grid;gap:7px}.unit-picker{flex:1;min-width:220px}.flash-tools select{font:inherit;color:var(--navy);border:1px solid #b7c9e1;border-radius:12px;background:white;padding:12px;min-height:48px;width:100%;max-width:100%}.flash-study{max-width:850px;margin:0 auto}.flash-study h2{font-size:1.15rem;margin:16px 0;color:var(--navy)}.flash-meta{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;font-size:.82rem;color:var(--muted);margin:14px 0}progress{width:100%;height:8px;accent-color:#17835a}.study-card{background:#fff;border:1px solid #cad8e9;border-top:5px solid var(--blue);border-radius:22px;padding:clamp(22px,4vw,38px);box-shadow:0 14px 38px #193e7510;min-height:300px;user-select:none;-webkit-user-select:none}.study-card h3{font-size:clamp(1.2rem,2.5vw,1.65rem);line-height:1.5;margin:14px 0 25px;color:var(--navy-dark)}.answer-panel{margin:20px 0;border-top:1px solid var(--line);padding-top:18px}.answer-panel p{font-size:1.08rem;line-height:1.7}.tip{background:#eff6fc;border-radius:12px;padding:14px;color:#344d6d}.tip p{font-size:.92rem;margin:5px 0}.watermark{font-size:.7rem;color:#617088;margin-top:25px;overflow-wrap:anywhere}.flash-actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:18px}.flash-actions button,.flash-tools button,.flash-study button{font-family:inherit;cursor:pointer;min-height:46px}.flash-actions .known{background:#12734d}.flash-navigation{display:flex;justify-content:space-between;margin:20px 0;gap:15px}.flash-main button:disabled{opacity:.45;cursor:default}.flash-main :focus-visible,.nav-list summary:focus-visible{outline:3px solid #e9aa35;outline-offset:4px}.flash-note{font-size:.78rem;color:var(--muted);line-height:1.7}.flash-sources{margin-top:24px;font-size:.82rem}.flash-sources a{display:inline-block;margin:12px 15px 0 0}.flash-status{min-height:24px;color:var(--navy);font-size:.9rem}.empty-card{background:white;border-radius:18px;padding:30px;text-align:center}.print-message{display:none}[hidden]{display:none!important}@media(max-width:650px){.flash-tools{display:block}.flash-tools label{margin-bottom:12px}.flash-actions button{flex:1}.study-card{min-height:260px}}@media print{body>*{display:none!important}body>.print-message{display:block!important;color:#111;background:white;padding:30px}}