Rather large difference in position between Mouse Pointer and mouse.x mouse.y

Further update,

launching Chrome in this mode:

--disable-gpu-vsync --disable-frame-rate-limit

Eliminates input lag at this site:

https://basro.github.io/input-lag-measuring-tool/

If you disable only one option or the other, you can see the lag goes down, suggesting they both, ultimately, play a role, though I would want to run a few more tests. However, it does seem that there must be an issue with how construct handles disabling v-sync and running full frames or something. Whatever way the mouse position gets reported to construct or however it is handled in construct seems to introduce a delay that does not exist in the above website, which once frames are unthrottled and vsync off, there is basically no discernible lag.

Also of importance is that if you simply use --disable-gpu-vsync at the above site, you also have only a teeny bit of lag, while construct still has a lot of visible lag, both running in the same chrome environment...

canvas.onmousemove = function(event) {
	var r = canvas.getBoundingClientRect();
 currPos.x = (event.clientX - r.left) * devicePixelRatio;
 currPos.y = (event.clientY - r.top) * devicePixelRatio;
}