Neat demo! I really liked the sprite of the main character, reminded me a bit of zero suit Samus in Zero Mission. The level and the music were pretty good too.
The gun was fun to use, and there was a nice sense of progression with the damage upgrades. The use of "ammo" for double jump and dashing is an interesting idea, but in practice I think it was a kind of an annoyance.
Regardless, good job!