Good little game! I enjoyed it :)
Other people said it already but a few collisions seem odd.
And I personally think it misses a pause panel, or a way to go back to the menu from the levels :)
Also an idea would be to make each colored slime have a special capacity, like a blue can be dragged, a purple can be bounce on, .... (just a thought, the game is pretty good like this ;) )
Good job!