I've played this a few times and it's pretty good.The death I had that was the most "contentious" was due to the blue square spawning so close to the edge of the screen and getting hit by the laser right when it came out.
I'm not sure if the alternative is limiting where the squares can spawn, making some sort of "warning" for an incoming laser or making the entire arena more like a boxing ring or an island in design (not aesthetically) so that there's an opportunity to see the laser appear but have that area be just outside the play area.
I didn't have much of a problem with the stock enemy, but it would be cool to have some variety. If you're using flashing as an indicator of impending detonation, maybe have an enemy type that'll stop, pivot to face the player's location while flashing, then charge one final time. Just to break up the kind of circular swarm with the one enemy type that goes on.