#physicsGradeApp{--pg-bg:#fff;--pg-side:#f7f7f8;--pg-ink:#202123;--pg-muted:#6b6f76;--pg-line:#e2e2e5;--pg-hover:#ececf1;--pg-blue:#456f98;--pg-blue-soft:#edf4fa;--pg-green:#23755d;--pg-radius:12px;position:relative;min-height:760px;background:var(--pg-bg);color:var(--pg-ink);font:15px/1.5 Arial,Helvetica,sans-serif;isolation:isolate}
#physicsGradeApp *{box-sizing:border-box}#physicsGradeApp [hidden]{display:none!important}#physicsGradeApp button{font:inherit}#physicsGradeApp button:focus-visible,#physicsGradeApp a:focus-visible{outline:3px solid #80a9cf;outline-offset:2px}
.pg-header{position:sticky;top:0;z-index:30;height:64px;display:flex;align-items:center;gap:18px;padding:0 22px;border-bottom:1px solid var(--pg-line);background:rgba(255,255,255,.96);backdrop-filter:blur(12px)}.pg-logo{display:flex;align-items:center;gap:10px;color:inherit;text-decoration:none}.pg-logo-mark{width:34px;height:34px;display:grid;place-items:center;border-radius:10px;background:#172b3d;color:#fff;font:700 19px Georgia,serif}.pg-logo strong{display:block;font-size:15px;letter-spacing:-.25px}.pg-logo small{display:block;color:var(--pg-muted);font-size:10px;letter-spacing:.06em;text-transform:uppercase}.pg-header-course{margin-left:auto;color:var(--pg-muted);font-size:12px}.pg-menu-button{display:none;border:1px solid var(--pg-line);border-radius:8px;background:#fff;padding:8px 11px;color:var(--pg-ink);cursor:pointer}
.pg-layout{display:grid;grid-template-columns:280px minmax(0,1fr);min-height:calc(100vh - 64px)}.pg-sidebar{position:sticky;top:64px;height:calc(100vh - 64px);display:flex;flex-direction:column;border-right:1px solid var(--pg-line);background:var(--pg-side)}.pg-sidebar-head{padding:20px 16px 12px}.pg-home-button{width:100%;display:flex;align-items:center;gap:10px;border:0;border-radius:9px;background:transparent;padding:11px 12px;color:var(--pg-ink);text-align:left;cursor:pointer}.pg-home-button:hover,.pg-home-button[aria-current=true]{background:var(--pg-hover)}.pg-home-icon{width:20px;text-align:center;color:var(--pg-muted)}.pg-nav{flex:1;overflow:auto;padding:0 10px 18px;scrollbar-width:thin}.pg-nav-label{padding:15px 12px 7px;color:var(--pg-muted);font-size:10px;font-weight:700;letter-spacing:.1em;text-transform:uppercase}.pg-topic{margin:3px 0}.pg-topic>summary{list-style:none;display:flex;align-items:center;gap:8px;padding:10px 12px;border-radius:9px;cursor:pointer;font-size:12px;font-weight:700}.pg-topic>summary::-webkit-details-marker{display:none}.pg-topic>summary::before{content:'›';width:14px;color:var(--pg-muted);font-size:18px;line-height:1;transition:transform .16s}.pg-topic[open]>summary::before{transform:rotate(90deg)}.pg-topic>summary:hover{background:var(--pg-hover)}.pg-module-title{padding:8px 12px 5px 34px;color:var(--pg-muted);font-size:10px;text-transform:uppercase;letter-spacing:.06em}.pg-lesson{width:100%;display:grid;grid-template-columns:24px minmax(0,1fr);gap:8px;border:0;border-radius:8px;background:transparent;padding:9px 10px 9px 25px;color:var(--pg-ink);text-align:left;cursor:pointer;font-size:12px;line-height:1.35}.pg-lesson:hover,.pg-lesson[aria-current=true]{background:var(--pg-hover)}.pg-lesson-number{color:var(--pg-muted);font-variant-numeric:tabular-nums}.pg-sidebar-foot{padding:15px 18px;border-top:1px solid var(--pg-line);color:var(--pg-muted);font-size:10px}.pg-backdrop{display:none}
.pg-main{min-width:0;padding:0 clamp(22px,4vw,64px) 70px}.pg-home{max-width:1040px;margin:0 auto}.pg-hero{padding:58px 0 42px;border-bottom:1px solid var(--pg-line)}.pg-eyebrow{margin:0 0 10px;color:var(--pg-blue);font-size:11px;font-weight:700;letter-spacing:.11em;text-transform:uppercase}.pg-hero h1{max-width:760px;margin:0;font:600 clamp(38px,5vw,64px)/1.06 Georgia,'Times New Roman',serif;letter-spacing:-.035em}.pg-lead{max-width:760px;margin:22px 0 0;color:#44474d;font:19px/1.65 Georgia,'Times New Roman',serif}.pg-actions{display:flex;flex-wrap:wrap;gap:10px;margin-top:27px}.pg-button{display:inline-flex;align-items:center;justify-content:center;min-height:42px;border:1px solid var(--pg-line);border-radius:9px;background:#fff;padding:10px 16px;color:var(--pg-ink);text-decoration:none;font-weight:700;font-size:13px;cursor:pointer}.pg-button:hover{background:var(--pg-side)}.pg-button-primary{border-color:#172b3d;background:#172b3d;color:#fff}.pg-button-primary:hover{background:#29465f}.pg-overview{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:28px 0}.pg-stat{padding:17px;border:1px solid var(--pg-line);border-radius:var(--pg-radius);background:#fff}.pg-stat strong{display:block;font-size:22px}.pg-stat span{color:var(--pg-muted);font-size:12px}.pg-section{padding:34px 0;border-bottom:1px solid var(--pg-line)}.pg-section h2{margin:0 0 8px;font-size:25px}.pg-section-intro{max-width:720px;margin:0 0 22px;color:var(--pg-muted)}.pg-path{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.pg-path-card{padding:20px;border:1px solid var(--pg-line);border-radius:var(--pg-radius)}.pg-path-card small{color:var(--pg-blue);font-weight:700;text-transform:uppercase;letter-spacing:.06em}.pg-path-card h3{margin:9px 0 8px;font-size:17px}.pg-path-card p{margin:0;color:var(--pg-muted);font-size:13px}.pg-principles{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}.pg-principle{padding:18px;background:var(--pg-side);border-radius:var(--pg-radius)}.pg-principle b{display:block;margin-bottom:6px}.pg-principle p{margin:0;color:var(--pg-muted);font-size:13px}
.pg-reader{max-width:1180px;margin:0 auto;padding-top:22px}.pg-reader-head{display:flex;align-items:flex-start;justify-content:space-between;gap:20px;padding:12px 0 18px;border-bottom:1px solid var(--pg-line)}.pg-reader-head p{margin:0 0 4px;color:var(--pg-blue);font-size:10px;font-weight:700;letter-spacing:.08em;text-transform:uppercase}.pg-reader-head h1{margin:0;font-size:24px;line-height:1.25}.pg-reader-close{flex:none;border:1px solid var(--pg-line);border-radius:8px;background:#fff;padding:8px 11px;color:var(--pg-muted);cursor:pointer}.pg-modes{position:sticky;top:64px;z-index:20;display:flex;gap:4px;margin:0 0 12px;padding:8px 0;background:rgba(255,255,255,.94);overflow:auto;backdrop-filter:blur(12px)}.pg-modes button{flex:none;border:0;border-radius:8px;background:transparent;padding:9px 13px;color:var(--pg-muted);cursor:pointer}.pg-modes button[aria-selected=true]{background:var(--pg-hover);color:var(--pg-ink);font-weight:700}.pg-frame{display:block;width:100%;height:700px;min-height:260px;border:1px solid var(--pg-line);border-radius:var(--pg-radius);background:#fff;transition:height .2s}.pg-sequence{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:15px 0}.pg-sequence button{border:0;background:transparent;padding:9px;color:var(--pg-blue);font-weight:700;cursor:pointer}.pg-sequence button:disabled{opacity:.3}.pg-sequence span{color:var(--pg-muted);font-size:11px}
@media(max-width:900px){.pg-layout{grid-template-columns:240px minmax(0,1fr)}.pg-main{padding-inline:24px}.pg-overview,.pg-principles{grid-template-columns:1fr}.pg-path{grid-template-columns:1fr}}
@media(max-width:720px){#physicsGradeApp{min-height:100vh}.pg-header{height:58px;padding:0 13px}.pg-menu-button{display:inline-flex}.pg-header-course{display:none}.pg-layout{display:block;min-height:calc(100vh - 58px)}.pg-sidebar{position:fixed;z-index:50;top:58px;bottom:0;left:0;width:min(310px,88vw);height:auto;transform:translateX(-102%);transition:transform .18s;box-shadow:12px 0 32px #0002}.pg-menu-open .pg-sidebar{transform:none}.pg-menu-open .pg-backdrop{display:block;position:fixed;z-index:40;inset:58px 0 0;border:0;background:#0006}.pg-main{padding:0 15px 50px}.pg-hero{padding-top:38px}.pg-hero h1{font-size:38px}.pg-lead{font-size:17px}.pg-reader{padding-top:10px}.pg-reader-head{display:block}.pg-reader-close{margin-top:12px}.pg-modes{top:58px;margin-inline:-15px;padding-inline:15px}.pg-frame{border-radius:8px}.pg-sequence span{display:none}}
@media(prefers-reduced-motion:reduce){.pg-sidebar,.pg-frame{transition:none!important}}
.pg-lesson.is-planned{color:#686d73}.pg-lesson.is-planned small{display:block;margin-top:3px;color:#8a9097;font-size:9px;font-weight:700;letter-spacing:.08em;text-transform:uppercase}
.pg-planned-panel{margin:24px 0;padding:42px 28px;border:1px solid var(--pg-line);border-radius:var(--pg-radius);background:var(--pg-side);text-align:center}.pg-planned-panel span{display:inline-block;margin-bottom:12px;border-radius:999px;background:var(--pg-blue-soft);padding:6px 10px;color:var(--pg-blue);font-size:10px;font-weight:700;letter-spacing:.08em;text-transform:uppercase}.pg-planned-panel h2{margin:0 auto 10px;max-width:680px;font-size:25px}.pg-planned-panel p{max-width:600px;margin:0 auto;color:var(--pg-muted)}