External store synchronization

<div class="scene"><div class="views"><div class="view">VIEW A<b id="a">0</b></div><div class="store">STORE<b id="store">0</b></div><div class="view">VIEW B<b id="b">0</b></div></div><div class="links"><span></span><span></span></div><div class="label" id="note">one snapshot, two subscribers</div></div>

.scene{width:min(94vw,800px);height:min(86vh,320px);position:relative;overflow:hidden;display:flex;flex-direction:column;justify-content:space-between;border:1px solid var(--line);border-radius:14px;background:var(--surface);padding:clamp(9px,2.4vmin,20px);font:500 clamp(15px,4vmin,18px)/1.3 var(--font-sans,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif)}.scene b,.scene strong{font-weight:700}.label{color:var(--muted)}.code{font-family:ui-monospace,SFMono-Regular,Consolas,monospace}.pill{border:1px solid var(--line);border-radius:8px;padding:.4em .65em;background:var(--bg)}.active{border-color:var(--accent)!important;color:var(--accent)!important;background:color-mix(in srgb,var(--accent) 10%,var(--surface))!important}.views{display:flex;align-items:center;justify-content:space-between;gap:5px;height:65%}.view,.store{width:30%;height:62%;border:1px solid var(--line);border-radius:8px;display:flex;align-items:center;justify-content:center;flex-direction:column}.store{border-color:var(--accent);color:var(--accent);background:var(--bg)}.views b{font:700 clamp(20px,6vmin,38px) ui-monospace,monospace}.links{display:flex;justify-content:space-around}.links span{width:30%;height:4px;background:var(--accent);border-radius:4px;animation:pulse 1.6s infinite alternate}@keyframes pulse{to{opacity:.2}}.label{text-align:center;margin-top:12px}

let n=0;function tick(){for(const id of ["a","b","store"])document.getElementById(id).textContent=n;document.getElementById("note").textContent="snapshot version "+n;n=(n+1)%5}tick();setInterval(tick,900)