I beat the game and found a bug (description below).
Very nice! And cute website itch.io. Puzzles also good and well thought out, it has to be a pleasure to make those. I wonder if the pacing of adding new elements is too fast? On the other hand, it's Jam and the game is surprisingly polished and has an awful lot to offer. Especially in the end with a "mushroom dynamic lights" hehe.
I found a bug! at this point in the video I can flip the light to the other side. If I'm not mistaken in another place later I can also cheat like this. 
Viewing post in Slime's Light jam comments
thank you. I was actually a bit worried that I wouldn't make enough levels or that they would be boring. Most of the time during the jam was spent programming a level editor.
And thanks for telling me about the skip. I did test each level when I made them, but stuff like that still got passed me. I think for that specific case, I added that doorway above to let the player in or out even if the lower door is locked. Plus the fact that items could get dropped/picked-up through doors doesn't help.