This is a good concept but it could be better, chasing enemies is good enough and erasing their bullets is good too, but there's the issue where you can just walk to the exit without attacking anyone xD, also, fighting squares is kinda boring.
Final boss is quite simple, but it's obvious you focused on visuals, so it was a nice experience as well.
PD: I couldn't run this well enough on chrome, its very laggy, I had to run it on firefox so it could run well.