Basically, what the other two reviews have said, I agree with.
Gameplay, 4/5: Simple, Very Basic, but Shows Promise
Already, perhaps because of bugs, but there's a sort of strat with jumping and shooting where you shoot faster if you shoot before landing, shoot while landing, and shoot while jumping all in a fast sequence (just spam jump and shoot like it's megaman).
Aside from dumb, basic strats, it's simple but is very responsive. I could see an expansion of skills or power ups for a more rouge-like system, or simple stat system for more dark-souls like. It has a solid foundation, where the dodge feels good, movement is good, but needs more depth, but will come in time. Even as is, if they add only a few more enemies, this barebones combat system would suffice. Maybe for a two hour game?
However, some basic things that are missing is an options menu in the main menu, or even in the pause menu, so you have to edit volume settings from the game maker options or from your PC's sound settings.
Basically, there's no problems other than it's super duper simple. Everything works well. Jumping is good (maybe could be a tad higher), rolling is responsive, moving and shooting is good.
Visuals, 5/5: Perhaps, a Bit Too Good...
The art is actually really nice. The environments, though the solid ground is a bit basic, is still very nice. The menu, though lacking an options menu from in-game, is still nice. Pop-ups, animations, etc. I just hope they can keep this quality with everything else, and with any future expansions.
Audio, 5/5: Custom Music (I believe)
It's all still a bit simple, but the sound effects like jumping, shooting, the enemy attacks, etc. are all good. I think the menu has unique music that I've never heard, and again, while simple, is very nice.
Story, N/A.
Basically... This is a very nice demo. Maybe a little bit too much effort and polish for what is the demo, but the very basic gameplay, the audio and art are all very nice. If this level of quality can be maintained throughout maybe 2 hours or so, an easy 5 star. Of course, there needs to be some basic quality of life things such as option menu in the main menu, control rebinding, etc.