pretty great game. Hdere are a couple of suggestions and comments.
The L and K controls didnt work for me, though, which was a buzzkill. im a WASD user at heart.
Lag didnt cause many issues in the puzzle levels, but i found it very difficult to get past some of the more difficult platforming levels where there were lots of rats to dodge.
Also, consider allowing the player to press space or another key to go to the next level, because it can be a bit tedious going from mouse to keyboard to progress when there are no mouse controls in the game.
By the 5th or 6th level, the pick up/throw button had kind of just stopped responding, which was infuriating during levels where the balls needed to be placed in particular places/kept out of others. i would walk up to it and press x, only to have it pushed away from me over a ledge or whatever else. I could get it to work, but it would sometimes take several restarts where i had made no mistakes.