Lol, the "save bunny" level (third ending) was a proper pain in the ass. But in a good, "wow, what a clever puzzle game" sort of way.
I can't figure out ending #1; I thought it may have been getting the thief with a purple skull on level 20 while they are splitting up, but after like 20 attempts--if this is the solution, you have to time it reeeeally tightly--I think it finally touched him and did nothing, so I gave up. The solution is probably something really simple and obvious, but a short "endings walkthrough" may have been a good addition for the completionists among us.
Rambling aside, great game and great puzzles!