The little suit-up transformation sequence was cute, hope you animate it properly sometime (or get someone to do it for you.)
I'm not sure I like the weapon subsystem as it is: I accidentally picked up a subweapon I didn't want halfway through the plant level and was stuck with it until the end. I would make it so you can cycle through the subweapons, with the ammo you pick up going to the active subweapon.
The vertical drift as you move horizontally is a bit annoying, made me hit a projectile or two. It's not a necessarily bad addition but I don't like it very much.
The crushers are a little buggy, sometimes I get crushed when I should have lived and survive when I should've died. I also got pushed into a wall by a crusher at one point.
I don't really get the setting of the game yet, why does RoboTemplar need to kill some blobby plant dudes again? Feels a little underwhelming, I was expecting aliens, monsters, or other robots who were threatening Earth or something.
Challenge rooms were cool, I took an embarrassing amount of time to complete the first crusher one.
Still eager to see how the game shapes up. Anyway, here's some quick art.