The concept itself sounds like it could be interesting and some aspects of the gameplay are cool. The problem for me is the fact that the game seems to be split on what it actually wants to be. On one hand your have the speedrun timer aiming for best times, when on the other hand you have features punishing speed.
A suggestion I'd make to make it a bit less punishing speed wise would be to have the bullets not be able to either leave the screen or come back into it when bouncing. Cause there were quite a few situations where I would have bullets from offscreen bouncing back in the midst of all the bullets I was shooting and I would have nearly no time to dodge them. Since I was moving that way.
Otherwise though I think some clarification on certain things would be nice. Like the fac tthat hte blocks seem to give health when destroyed with the green bullets ? I'm not sure if that's correc though because I also had something happen at some point that lead to me losing most of my health after that.
One final thing would be the lack of feedback, it lead to a lot of situations where I had no idea what I did wrong, which ends up making it a little more annoying since there's no clear indication waht to improve on.
Overall though an interesting concept and it seems like a very different mix of mechanics, that I feel are just a bit too punishing in some regards, but ignoring that it does lead to some good frantic gameplay trying ok handle everything going on. I just wish there were less deaths out of your control.