That was fun, good gameplay and enjoyable music. The graphics perhaps weren't as cohesive as they could have been (there were pixels of varying sizes) but I liked the gun particles. The controls worked well, never needed the dash though.
Some comments about the map. I had no idea what was the point of the red doors before reading other comments, I also thought there would be a red gun because that's how all the other doors worked. I also encountered a pitch-black room that I couldn't even go back from and had to load a save (to the right from the double jump). You also seemed to have the same problem as I did - a big map but no time to create a map system. More difficult enemies could have also begun to appear as the guns became more powerful as well.
While the map was a bit unclear, I still enjoyed the game, cheers!