The core idea is good. but i would definitely change the controls on a keyboard. Space for shooting and K for jumping felt unintuitive. i would switch them, so that the right hand handles shooting and the left one movement. I would then also move the aim up and down to the right hand. Maybe even instead of having to press shoot and aim up / down have one button for shooting in each direction, like K for straight, I for up and "," for down. Aside from the controls i enjoyed the demo. Great work.
Also for the demo maybe add a place where you are required to slide to continue. I never used it because i totally forgot i could. That would then obviously require some form of ingame tutorial. Maybe you could write "down + k" to slide (or "down + space" with my suggestions :D) on the background wall.