Hi!
VERY SOLID entry. I love those platformer puzzles that challenge specifically my ability to maneuver through the mechanics. In terms of mechanics, this was the most solid entry I played.
I missed the application of the jam's theme: Giant Monster Foot and Maze, though.
I loved the graphics. You went full minimalistic but took the time to actually design shapes that communicate the objects' behavior (like the bullets being triangles in contrast with the character being a square, meaning that the bullets are dangerous and would hurt the character).
I also missed some SFX and BGM, but I can't say much since my own entry doesn't have those as well.
This entry could definitely make some use of moving platforms as well and I see a lot of potential for a casual audience. I have a friend that launched a similar game for this niche, if you want to I can connect you guys so he can give you some insights about his game performance and what you can expect if you decide to release a full version of it, his game is Steve is Alone.
Here's my play session of your game: