Fluid Paint
This is awesome, but my immediate reaction is: it would be better without the browser.<p>On my MacBook Pro (Retina 15 inch 2015, "the best laptop ever made"), it's just laggy enough to be a bit irritating. A native app would be wonderful.<p>Edit: Just to be sure, I use Firefox, but it doesn't seem to be a Firefox only -effect, as it's similarly laggy on Chrome too.