.app-page{min-height:calc(100svh - 78px);padding:42px clamp(16px,5vw,70px) 70px;background:linear-gradient(145deg,#f7fbff,#eef5ff)}.app-page[hidden]{display:none}.page-head{text-align:center;max-width:850px;margin:0 auto 25px}.page-head h1,.chapter-head h1{margin:5px 0;font-size:clamp(2rem,5vw,3.5rem);letter-spacing:-.04em}.page-head p{color:#5f6c84}.crumbs{display:flex;gap:9px;align-items:center;flex-wrap:wrap;max-width:1320px;margin:0 auto 15px;color:#60708a}.crumbs a{color:#075ee8;font-weight:750;text-decoration:none}.selection-shell,.resource-panel,.about-shell{max-width:1320px;margin:auto;padding:clamp(16px,3vw,32px);border:1px solid #dae6f5;border-radius:22px;background:#fff;box-shadow:0 15px 45px rgba(28,65,127,.1)}.option-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:17px}.option{display:flex;align-items:center;gap:15px;min-height:96px;padding:18px;border:1px solid #dce7f5;border-radius:15px;color:#071b5a;background:linear-gradient(135deg,#fff,#f3f8ff);text-decoration:none;transition:.18s}.option:hover{transform:translateY(-2px);box-shadow:0 8px 18px rgba(20,70,150,.1)}.option-icon{display:grid;place-items:center;flex:0 0 52px;height:52px;border-radius:13px;background:#e5f1ff;font-size:28px;font-weight:850}.option strong,.option small{display:block}.option small{margin-top:4px;color:#68748a}.chapter-head{max-width:1320px;margin:18px auto;display:flex;align-items:end;justify-content:space-between;gap:15px}.tabs{display:flex;max-width:1320px;margin:0 auto 15px;gap:10px}.tab{padding:13px 18px;border:1px solid #b9cdef;border-radius:10px;color:#071b5a;background:#fff;font-weight:800;cursor:pointer}.tab.active{color:#fff;border-color:#075ee8;background:#075ee8}.resource-panel{min-height:340px}.reader-top{display:flex;justify-content:space-between;gap:12px;margin-bottom:16px;color:#5f6d85}.pdf-pages{display:grid;justify-content:center;gap:20px}.pdf-pages canvas{max-width:100%;height:auto;border-radius:4px;box-shadow:0 4px 20px rgba(0,25,70,.18)}.video-parts{display:flex;gap:9px;margin-bottom:14px}.video-part{padding:9px 14px;border:1px solid #b9cdef;border-radius:8px;background:#f7faff;color:#071b5a;font-weight:750}.video-part.active{background:#075ee8;color:#fff}.video-box{position:relative;padding-top:56.25%;border-radius:15px;overflow:hidden;background:#06163e}.video-box iframe{position:absolute;inset:0;width:100%;height:100%;border:0}.empty{text-align:center;padding:45px;color:#60708a}.about-shell img{display:block;width:100%;height:auto;border-radius:12px}.view-hidden{display:none!important}@media(max-width:900px){.option-grid{grid-template-columns:repeat(2,1fr)}}@media(max-width:600px){.app-page{padding-top:26px}.option-grid{grid-template-columns:1fr}.chapter-head{align-items:flex-start;flex-direction:column}.reader-top{flex-direction:column}.tabs{overflow:auto}.tab{white-space:nowrap}.resource-panel{padding:10px}}