Well done! I really liked the gameplay once I realized what triggers the explosion. Good audio also.
I think the prompt to "clear the way" in 2nd level should be more along the lines of "The specimen explodes if it touches any boxes. Kick the boxes." It probably would be sufficient explanation for what happens and how it can be avoided. Of course, some visual and auditory reaction when they get crushed by the specimen wouldn't hurt either. The separate cancel button was kinda awkward as others have said.