I partly take one thing back. It seems the blue dot can't pick up red dots on the side edges once it reaches a certain size. 5 or 6. Once it gets a noticeable black border on it. So I think the hit box always has to be at least as big as the barrier edge. Probably not a big deal though. Drain can take care of a few that get through inevitably.
Oh I thought that would make me lose upgrade points. I'll try that. I know some games go fullscreen without their proportions getting distorted so it would have large black areas on the sides or left and right. I don't know if that is hard to program. Maybe it's not worth it but that was the only thing I found frustrating is constantly going off the edges. But idk if it doesn't bother other players it may be just me. Or it could improve player experience. One of those. Improvement or just me.