The main problem I've had with the Tapa player is in fact exactly that I can't erase squares reliably. When I click on them there is a ~50% chance whether they empty or stay filled. Doesn't this affect everyone? I've only used Chrome, but I can't be the only one.

I also had to stop using the different colours because for whatever reason I found them so different in hue that my eye didn't "see" 2x2s or notice whether they were connected together - I've made literally hundreds of incorrect submissions. :)