Your screenshots looked great. Unfortunately, I was playing entries on my laptop where I don't have GMS2 installed. It would have been better if you put a zipped EXE for your entry. I'll check back with this entry later if you can do an update.

Nice colors, but try to keep the size of pixels consistent between sprites. :)

I liked the proposal! I see that a lot of effort was put into that graphics, nicely done! I've some suggestions and recommendations that I think will improve the game experience. Small changes that makes a lot of difference.

1. In the game maker, you can export an executable for your game, making your game accessible for those who don't have Game Maker installed. You go into Build->Create executable and choose the type of package you want (a zip file or a installer);
2. Teach the players how to play the game, by giving them instructions or making the level design intuitive;
3. If the character shoots, get hit or hits an enemy, put some correspondingly sound effects (in the internet, search for websites that have sound effects in public domain, in case you can't make them);
4. Its not a rule but... I'd advise making the art for the protagonist before making the enemies. Because the player will be playing with the protagonist, so it's important! 

Good job!

Interesting idea, weak prototype.

Good luck in development =)

Not sure if it was intentional but you can infinitely jump higher? Either way, I like the idea of switching between different bodies. I think that if the game was a little more fast paced, I could have gotten a little more usage out of switching. At this point, I felt I was able to do pretty well with just the shooting body and jumping in mid air to avoid most of the enemies. I really did like the idea of the shield body but the amount of enemies + speed didn't make it super necessary to use. However, playing this survival game and switching between modes is a really neat concept! Nice work!