Collision detection can be a bit finicky at times (such as when enemies are inside a timed door as it closes), but otherwise this is a pretty well executed little puzzler. I love the slime mechanic in particular: the fact that it's technically introduced right at the start but isn't forced by the level design until way farther in makes observant players feel rewarded.

The bosses feel like they should be switched around: Boss #2 is static in difficulty, while Boss #1 gets harder as the fight goes on, so Boss #1 feels much more like a final boss than Boss #2.

Also, the timer is broken: you can easily get game completion times of <1s by just starting the game, immediately exiting to the main menu, and loading up the final boss. I know there's no global high score table so it doesn't really matter at the moment, but the fact that the timer breaks so frequently when menu-ing or restarting a level is annoying even for just self-timing a speedrun.

Para que pueda abrir o cerrar alguna de las puertas se demora en tomar la acción, en ocasiones debo presionar la tecla varias veces.

Looks pretty nice, simple controls and fitting music.
There's something that this game should have : A restart level option.
One can get into a situation where there's no possible moves to make. On the box operated switches levels you can get stuck with no other option but restart the hole game if one doesn't think very carefully every single move.
As an example : cornering a box