.em{--paper:#F6F8FC;--sheet:#FFFFFF;--ink:#1B2233;--muted:#5A6378;--rule:#D9DEEA;--vert:#2F3E9E;--perp:#0E7C74;--hi:#B45309;--tint:#EEF1FA;background:var(--paper);color:var(--ink)}.em *,.em :after,.em :before{box-sizing:border-box}.em article{--serif:"Frank Ruhl Libre","David","Times New Roman",serif;--ui:Assistant,Arial,sans-serif;font-family:var(--serif);font-size:1.13rem;line-height:1.75;display:none}.em article.on{display:block}.em article[data-lang=ar]{--serif:Amiri,"Traditional Arabic","Times New Roman",serif;--ui:"Noto Sans Arabic",Tajawal,Tahoma,Arial,sans-serif;font-size:1.22rem;line-height:1.95}.em article[data-lang=en]{--ui:Assistant,"Helvetica Neue",Arial,sans-serif}.em-bar{background:var(--paper);border-bottom:1px solid var(--rule)}.em-bar-in{max-width:44rem;margin:0 auto;padding:.6rem 1.25rem;gap:.6rem;justify-content:space-between}.em-bar-in,.em-crumb{display:flex;align-items:center;flex-wrap:wrap}.em-crumb{font-family:Tajawal,Noto Sans 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div{background:var(--tint);border-radius:4px;padding:.5rem .3rem}.em .readout b{display:block;font-size:1.35rem;direction:ltr;font-family:Assistant,Arial,sans-serif}.em .readout span{font-size:.85rem;color:var(--muted)}.em .lab p.hint{color:var(--muted);margin:.2rem 0 .6rem}.em .lab p.hint,.em button.reset{font-family:var(--ui);font-size:.95rem}.em button.reset{background:none;border:1px solid var(--rule);color:var(--ink);border-radius:4px;padding:.35rem .9rem;margin-top:.7rem;cursor:pointer}.em a:focus-visible,.em button:focus-visible,.em summary:focus-visible{outline:3px solid var(--vert);outline-offset:2px}.em .exercise{border:2px solid var(--ink);border-radius:4px;padding:1.3rem 1.4rem;margin:1.6rem 0;background:var(--sheet)}.em .exercise .tag{font-family:var(--ui);font-weight:700;margin:0}.em details{border-top:1px solid var(--rule);margin-top:1rem;padding-top:.6rem}.em summary{font-family:var(--ui);font-weight:700;cursor:pointer;color:var(--vert)}.em details[open] summary{margin-bottom:.4rem}.em footer{margin-top:3rem;border-top:3px double var(--rule);padding-top:1rem;font-family:var(--ui);color:var(--muted);font-size:.95rem}.em-more{max-width:44rem;margin:0 auto;padding:0 1.25rem 3rem;font-family:Tajawal,Noto Sans Arabic,sans-serif}.em-more a{color:var(--vert);font-weight:700;text-decoration:none}.em-more a:hover{text-decoration:underline}@media (max-width:520px){.em article{font-size:1.05rem}.em article[data-lang=ar]{font-size:1.14rem}.em .exercise,.em .theorem{padding:1rem}.em ol.em-steps>li{-webkit-padding-start:2.4rem;padding-inline-start:2.4rem}.em .em-page{padding-top:1.6rem}}