A more cave-like, brownish-reddish, underground Dungeon would be a really useful addition! If you go that direction, you could revise the current Dungeon tileset to be more of a polished above-ground Castle.

This game looks great, I want to play it from the GIFs alone. I'm seeing a strong Yoshi's Island influence in the palette and graphical style. The gameplay looks simple in a good way, and I would want to play more just to see what new gimmicks you throw at the player.

The player sprite is my least favorite thing-- the default face looks less polished than the other sprites.

I really like the artstyle of this game! I'm looking forward to its development.

I played the demo, the character moves at a nice comfortable pace and feels easy to control. The player and enemy sprites are all clear and easy to read although the explosion graphics' smooth scaling felt a little out of place with the pixel aesthetic.

I also encountered some weird behavior with the drop-through ledges. If I walked off of one to the side and immediately turned back around, I'd get pushed back on top of the platform instead of continuing down. And putting drop-through platforms above some of the instant-death gears instead of solid platforms is kind of mean...