.bg-guide{--bg-ink:#14233e;--bg-muted:#53627b;--bg-accent:#4936da;--bg-line:#dfe4ed;background:#f6f7fc;color:var(--bg-ink);padding:28px 20px 48px;font-family:Poppins,system-ui,sans-serif;line-height:1.75}
.bg-guide *{box-sizing:border-box}.bg-wrap{max-width:1180px;margin:auto}.bg-guide a{color:#4030bf;text-decoration:underline;text-underline-offset:3px}.bg-guide a:focus-visible,.bg-guide summary:focus-visible{outline:3px solid #8e7bf5;outline-offset:5px}.bg-breadcrumb{display:flex;flex-wrap:wrap;gap:12px;font-size:.85rem;margin-bottom:28px}.bg-hero{display:grid;grid-template-columns:minmax(0,1fr) 280px;gap:46px;align-items:center;padding:36px 0 40px}.bg-kicker{color:#6554c4;font-size:.73rem;font-weight:700;letter-spacing:.09em;display:block;margin-bottom:12px}.bg-hero h1{font-size:clamp(2rem,3.8vw,3.4rem);line-height:1.13;font-weight:800;letter-spacing:-.035em;margin:0 0 22px}.bg-lead{font-size:1.14rem;line-height:1.7}.bg-byline,.bg-small{font-size:.83rem;color:var(--bg-muted)}.bg-actions{display:flex;flex-wrap:wrap;gap:12px;margin-top:25px}.bg-guide a.bg-button{display:inline-flex;justify-content:center;align-items:center;gap:10px;background:var(--bg-accent);color:#fff;border:1px solid var(--bg-accent);border-radius:10px;padding:12px 18px;text-decoration:none;font-weight:600;font-size:.9rem;line-height:1.5}.bg-guide a.bg-outline{color:var(--bg-accent);background:transparent}.bg-summary{background:#19284c;color:white;border-radius:20px;padding:28px;box-shadow:12px 12px 0 #e5dfff}.bg-summary>span{font-size:.7rem;letter-spacing:.13em;color:#c8c0ff}.bg-summary strong{display:block;font-size:2rem;line-height:1.2;margin:22px 0}.bg-summary ul{padding-left:20px;font-size:.9rem}.bg-summary small{color:#d2daf0}.bg-toc{display:flex;flex-wrap:wrap;gap:10px 22px;border-top:1px solid var(--bg-line);border-bottom:1px solid var(--bg-line);padding:20px 0;margin:16px 0 40px;font-size:.85rem}.bg-layout{display:grid;grid-template-columns:minmax(0,1fr) 260px;gap:48px}.bg-content{min-width:0}.bg-content>section{margin-bottom:48px;scroll-margin-top:30px}.bg-guide h2{font-size:1.65rem;font-weight:750;line-height:1.3;letter-spacing:-.02em;margin:0 0 20px}.bg-guide h3{font-size:1.09rem;font-weight:700;line-height:1.5;margin:20px 0 12px}.bg-guide li{margin-bottom:8px}.bg-note{background:#eeebff;border-left:4px solid #7864e7;border-radius:0 12px 12px 0;padding:20px 22px;margin:24px 0}.bg-note p:last-child{margin-bottom:0}.bg-weeks{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:24px}.bg-weeks>div{border:1px solid var(--bg-line);border-radius:12px;padding:22px;background:#fff}.bg-weeks span,.bg-tag{font-size:.7rem;letter-spacing:.065em;font-weight:700;color:#6653bc}.bg-weeks h3{margin:10px 0}.bg-weeks p{font-size:.9rem;margin:0}.bg-exercise{border:1px solid var(--bg-line);border-radius:14px;background:#fff;padding:25px;margin:20px 0;scroll-margin-top:28px}.bg-exercise h3{margin:10px 0 14px;font-size:1.2rem}.bg-exercise p{overflow-wrap:anywhere}.bg-formula{font-family:Georgia,serif;font-size:1.2em;white-space:normal}.bg-exercise details{margin-top:22px;border-top:1px solid var(--bg-line);padding-top:15px}.bg-exercise summary{cursor:pointer;font-weight:650;color:#4431bf;list-style-position:inside}.bg-solution{padding-top:18px}.bg-solution ol,.bg-solution ul{padding-left:24px}.bg-error{color:#59657b;font-size:.88rem;border-left:3px solid #d8cffc;padding-left:14px;margin-top:18px}.bg-exercise blockquote{border-left:3px solid #8a78dc;background:#f4f1fc;padding:18px 22px;font-size:.96rem;margin:20px 0;color:#34435e}.bg-course{padding:30px;background:#eae7ff;border-radius:16px}.bg-course-links{display:grid;grid-template-columns:1fr;gap:10px;margin:22px 0}.bg-course-links a{display:flex;justify-content:space-between;border:1px solid #d4ccef;background:#fff;border-radius:8px;padding:12px 15px;text-decoration:none}.bg-course .bg-small{margin-top:20px;margin-bottom:0}.bg-side>div{position:sticky;top:24px;background:white;border:1px solid var(--bg-line);border-radius:16px;padding:24px}.bg-side h2{font-size:1.35rem}.bg-side p{font-size:.9rem}.bg-side .bg-button{width:100%}.bg-back{display:block;font-size:.8rem;margin-top:20px}.bg-sources li{font-size:.9rem;margin-bottom:15px}.bg-end{display:flex;justify-content:space-between;gap:18px;flex-wrap:wrap;border-top:1px solid var(--bg-line);padding-top:24px;font-size:.85rem}
@media(max-width:960px){.bg-layout{grid-template-columns:minmax(0,1fr)}.bg-side{display:none}.bg-hero{grid-template-columns:minmax(0,1fr) 240px;gap:30px}.bg-summary{padding:23px}}
@media(max-width:640px){.bg-guide{padding:20px 18px 36px}.bg-hero{grid-template-columns:minmax(0,1fr);gap:24px;padding:12px 0 25px}.bg-hero h1{font-size:2.05rem;line-height:1.16}.bg-lead{font-size:1.02rem}.bg-summary{box-shadow:6px 6px 0 #e5dfff}.bg-summary strong{font-size:1.6rem}.bg-weeks{grid-template-columns:1fr}.bg-toc{margin-bottom:30px}.bg-guide h2{font-size:1.42rem}.bg-exercise{padding:20px 17px}.bg-exercise blockquote{padding:15px}.bg-course{padding:23px 20px}.bg-actions{display:grid;grid-template-columns:1fr}.bg-content>section{margin-bottom:36px}.bg-sources ul{padding-left:21px}}
.bg-equation{display:block;overflow-wrap:anywhere;font-family:Georgia,serif;font-size:1.13em;line-height:1.9;margin:16px 0;padding:12px 16px;background:#f6f4fd;border-radius:8px}.bg-options{padding-left:27px;margin:20px 0;overflow-wrap:anywhere}.bg-options li{padding-left:5px}.bg-diagram{max-width:350px;margin:22px auto}.bg-diagram svg{display:block;width:100%;height:auto;background:#fafbff;border-radius:10px}.bg-diagram figcaption{font-size:.78rem;line-height:1.6;color:#53627b;margin-top:9px}.bg-reading{background:#eeebff;border-left:4px solid #7864e7;padding:20px 23px;border-radius:0 12px 12px 0;margin:25px 0}.bg-reading h3{margin-top:0}
@media print{.bg-side,.bg-actions,.bg-toc,.bg-end{display:none}.bg-guide{background:white;padding:0}.bg-hero,.bg-layout{display:block}.bg-summary{display:none}.bg-exercise{break-inside:avoid}.bg-exercise details:not([open]){display:none}.bg-guide a{color:inherit}}