The upgrade system is nice. I missed it on the first attempt. I've seen the screenshot and decided to try again to get that "movement speed" upgrade, but could not find it. Otherwise the second jump over the gap on the last "bridge" is not possible, I think.
Some notes: You have used the cyan markers both for directional hints and for decoration. Probably should be only used for directions.
The jump key buffering is too long, you can press jump anywhere in the air and he will jump when reaching ground.
The gray floor blocks were hard to see, I'd give the top face a different color than the rest to make it more distinguishable.
The crosshair did not help much as the bullets never hit that point, especially in the beginning. Later with several splits, you are hitting everything anyway. ^^