:root{--v2-shell-top:84px;--v2-rail-width:56px;--v2-rail-btn-tap:44px;--v2-rail-icon-size:18px;--v2-rail-btn-radius:10px;--v2-rail-gap:4px;--v2-rail-padding:4px;--v2-badge-size:16px;--v2-badge-font:10px;--v2-library-drawer-width:clamp(320px, 34vw, 520px);--v2-media-drawer-width:clamp(320px, 34vw, 540px);--v2-drawer-duration:500ms;--v2-drawer-ease:cubic-bezier(0.22, 1, 0.36, 1);--v2-backdrop-duration:220ms;--v2-backdrop-ease:cubic-bezier(0.2, 0.8, 0.2, 1)}.lesson-v2-shell{position:relative;display:flex;flex-direction:column;flex:auto;min-height:0}.lesson-v2-shell>.lesson-container.lesson-v2{flex:auto;min-height:0}html.has-lesson .lesson-container.lesson-v2{position:relative;display:grid;grid-template-columns:var(--v2-rail-width)minmax(0,1fr)var(--v2-rail-width);grid-template-rows:1fr;min-width:0;min-height:0;align-items:stretch;background:radial-gradient(circle at 18% 12%,rgba(34,197,94,8%),transparent 45%),radial-gradient(circle at 86% 20%,rgba(59,130,246,6%),transparent 40%),var(--bg)}html.has-lesson .lesson-v2 .v2-side-rail,html.has-lesson .v2-side-rail{grid-column:1;grid-row:1;align-self:stretch;flex:0 0 var(--v2-rail-width);width:var(--v2-rail-width);min-width:var(--v2-rail-width);max-width:var(--v2-rail-width);min-height:0;height:100%;border-right:1px solid rgba(15,23,42,8%);box-shadow:inset -1px 0 rgba(255,255,255,.35);background:linear-gradient(180deg,rgba(255,255,255,.92) 0%,rgba(248,250,252,.9) 100%);display:grid;grid-template-columns:1fr;grid-auto-flow:row;grid-auto-rows:min-content;justify-items:center;align-content:start;gap:var(--v2-rail-gap);padding:var(--v2-rail-padding);overflow:hidden;z-index:200;opacity:1;visibility:visible}html.has-lesson .lesson-v2 .v2-rail-btn,html.has-lesson .v2-rail-btn{display:flex;align-items:center;justify-content:center;position:relative;grid-column:1;width:var(--v2-rail-btn-tap);height:var(--v2-rail-btn-tap);border:1px solid transparent;border-radius:var(--v2-rail-btn-radius);background:0 0;color:#64748b;font-size:var(--v2-rail-icon-size);cursor:pointer;transition:border-color .18s ease,color .18s ease,background .18s ease,transform .15s ease}.v2-rail-badge{position:absolute;top:-5px;right:-5px;min-width:var(--v2-badge-size);height:var(--v2-badge-size);padding:0 4px;border-radius:999px;font-size:var(--v2-badge-font);font-weight:700;display:flex;align-items:center;justify-content:center;color:#fff;background:#64748b;border:1px solid rgba(255,255,255,.75);box-shadow:0 1px 4px rgba(0,0,0,.12)}html.has-lesson .lesson-v2 .v2-rail-btn:hover,html.has-lesson .lesson-v2 .v2-rail-btn.is-active,html.has-lesson .v2-rail-btn:hover,html.has-lesson .v2-rail-btn.is-active{color:#0f172a;border-color:rgba(59,130,246,.2);background:rgba(59,130,246,.12);transform:translateY(-1px)}.v2-rail-btn--empty{opacity:.3;cursor:default}.v2-rail-btn--empty:hover{color:#64748b!important;border-color:transparent!important;background:0 0!important;transform:none!important}.v2-rail-btn.v2-rail-alert{color:#ef4444;animation:rail-alert-pulse 2s ease-in-out infinite}@keyframes rail-alert-pulse{0%,100%{color:#ef4444}50%{color:#fca5a5}}.v2-rail-toast{position:fixed;transform:translateY(-50%)translateX(20px);background:rgba(0,0,0,.85);color:#fff;padding:8px 14px;border-radius:8px;font-size:13px;white-space:nowrap;z-index:9999;opacity:0;transition:transform .3s ease,opacity .3s ease;pointer-events:none}.v2-rail-toast.visible{transform:translateY(-50%)translateX(0);opacity:1}.v2-library-overlay{position:fixed;left:var(--v2-rail-width,56px);right:var(--v2-rail-width,56px);top:var(--v2-shell-top,84px);bottom:0;z-index:120;pointer-events:none;overflow:hidden}.v2-library-overlay.is-open{pointer-events:auto}.v2-library-backdrop{position:absolute;inset:0;border:0;padding:0;margin:0;background:rgba(15,23,42,.18);opacity:0;transition:none}.v2-library-overlay.is-open .v2-library-backdrop{opacity:1}.v2-library-drawer{position:absolute;top:0;left:0;width:var(--v2-library-drawer-width);height:calc(100vh - var(--v2-shell-top,84px) - 12px);max-height:calc(100vh - var(--v2-shell-top,84px) - 12px);height:calc(100svh - var(--v2-shell-top,84px) - 12px);max-height:calc(100svh - var(--v2-shell-top,84px) - 12px);height:calc(100dvh - var(--v2-shell-top,84px) - 12px);max-height:calc(100dvh - var(--v2-shell-top,84px) - 12px);border-radius:0 14px 14px 0;box-shadow:12px 12px 34px rgba(0,0,0,.18);border:1px solid var(--border-soft);overflow:hidden;background:var(--surface);visibility:hidden;transform:translate3d(-100%,0,0);transition:none;will-change:transform;contain:layout style}.v2-library-drawer.is-open{visibility:visible;transform:translate3d(0,0,0);transition:none}html.has-lesson .lesson-v2 #document-right-wrapper{grid-column:2/3;grid-row:1;display:flex;flex:auto;width:100%;min-width:0;overflow:hidden;padding-right:0;transition:padding-right 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8px}.v2-media-picker-list::-webkit-scrollbar{width:8px}.v2-media-picker-list::-webkit-scrollbar-track{background:rgba(148,163,184,.1);border-radius:8px}.v2-media-picker-list::-webkit-scrollbar-thumb{background:rgba(100,116,139,.45);border-radius:8px}.v2-media-picker-list::-webkit-scrollbar-thumb:hover{background:rgba(71,85,105,.65)}.v2-media-picker-list .v2-library-entry .file-button{width:100%;margin-bottom:3px;border-radius:7px}.v2-media-picker-list .file-button.active{background:rgba(59,130,246,.1);border-color:rgba(59,130,246,.25);color:var(--text)}.v2-media-picker-empty{font-size:12px;color:var(--muted);padding:8px 4px;text-align:center}.v2-media-content{flex:auto;min-height:0;position:relative;display:flex;align-items:center;justify-content:center;padding:8px}.v2-media-content 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12px}.v2-library-list::-webkit-scrollbar{width:10px}.v2-library-list::-webkit-scrollbar-track{background:rgba(148,163,184,.14);border-radius:8px}.v2-library-list::-webkit-scrollbar-thumb{background:rgba(100,116,139,.55);border-radius:8px}.v2-library-list::-webkit-scrollbar-thumb:hover{background:rgba(71,85,105,.72)}.v2-library-group{position:sticky;top:-8px;z-index:1;font-size:10px;font-weight:700;color:var(--muted);text-transform:uppercase;letter-spacing:.04em;padding:7px 6px 5px;background:var(--surface)}.v2-library-entry .file-button{width:100%;margin-bottom:4px;border-radius:8px}.v2-library-empty{font-size:13px;color:var(--muted);padding:10px 6px}@media(prefers-reduced-motion:reduce){html.has-lesson .v2-library-backdrop,html.has-lesson .v2-library-drawer,html.has-lesson .v2-media-drawer,html.has-lesson .v2-timer-drawer,html.v2-transitions-ready .v2-library-backdrop,html.v2-transitions-ready .v2-library-drawer,html.v2-transitions-ready .v2-media-drawer,html.v2-transitions-ready .v2-timer-drawer{transition-duration:1ms!important;transition-delay:0ms!important}}@supports(backdrop-filter:blur(8px)) or (-webkit-backdrop-filter:blur(8px)){.lesson-v2 .v2-side-rail,.v2-side-rail{backdrop-filter:blur(8px);-webkit-backdrop-filter:blur(8px)}}@supports not ((backdrop-filter:blur(8px)) or (-webkit-backdrop-filter:blur(8px))){.lesson-v2 .v2-side-rail,.v2-side-rail{background:linear-gradient(180deg,rgba(255,255,255,.98) 0%,rgba(248,250,252,.96) 100%)}}