That's because that demo is using SVG for graphics and hence updating 300+ DOM elements every frame will of course start stuttering... Once I've updated that example to use the hdom-canvas support lib (https://github.com/thi-ng/umbrella/blob/master/packages/hdom...) this will be a non-issue. E.g. here's another demo which draws 10k rectangles @ 60fps. Only once I go >25K, I'm starting to loose framerate (MBP 2016):

https://demo.thi.ng/umbrella/hdom-canvas-shapes/#points-10k https://demo.thi.ng/umbrella/hdom-canvas-shapes/#points-50k