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1: If you ever go off a lift (thing that sends you flying diagonally), and keep holding which ever direction you're going, once you run into a wall you'll be sent flying to the top of the ledge. Even if that happens to be the top of the level. And once on the top you can effectively freeze the entire game.

2: In the level "Shaft", on the slope to the left, if you jump in the right place, you can freeze the game. Same goes for the first slope on the right. Except, in reverse: if you DONT jump at the right time you will possibly freeze the game. Apparently people have had this problem also.

3: The last level "Credits" is SO buggy, that I'm surprised I beat it. Well, actually only one spot on the level doesn't work, but it's SUCH a bother: there's this one block that is, I'm guessing, supposed to be hidden, and when you press a button it slides out. For me it started out closing the area off, so when you went up the series of notches in the wall to the block, you would either be sent to the left a while, or sent to the top of the block.
The first couple of times I did this, I got sent to the left, and on the third time I got sent directly above the block. Besides that I had no more problems with the level.

4: The shift key. As RemmK mentioned, if you press the shift key, you'll be "dropped" out of the level. For me, it sent me to the previous level. And if I held it, it would rapidly cycle through them, until it reached the end and "beyond". At which point the game would (you guessed it!) freeze.

5: Sometimes when I entered a level one or more of my guys would start out in the "hanging on a ledge" position. One could just jump out of this. So it's not that bad.

Besides all of these things, I really like the game, and I think you should make a sequel. (Preferably with an "exit level" button.)

Final Score: 6/10