That's a lovely take on the runner genre !
Here's small tips, those are personal opinions so feel free to not apply them ;D
- Don't restart the music when we die. That wait we can hear more than a few seconds of it
- Make the difficulty less instantaneous. Like having the gunner ennemy appear only after x score for exemple. Or even speed up the game after a while too
- Having the possibility to switch mid-air
- Turn the JUICE to eleven. Like have impact when killing an ennemy, blood going everywhere, a sound effect, a small time stop (1 or 2 frames) to feel like it's something heavy. This will really make the player feel more fun when playing, even though nothing changed gameplay wise
- Of course, having more obstacle types and maybe different worlds with different character, each with their own abilities. I'm sure you already have a lot of ideas for that ;)
Anyway, this is a pretty good entry. Well done !