Great game! :) I found a 3 second method for beating level 16.
Before:
After:
The two blocks on the left aren't needed.
Also, how do I go into the sandbox mode I see so many people in?
Hey! I believe the sandbox mod you’re talking about is mystic mod. You should be able to download it from the link in the description of this video, however I am not totally sure whether this is the newest version of the mod and I have not had a chance to test the .exe file yet as I do not have access to a PC. Therefore I would proceed with caution just in case.