Not really broken, but broke out of. I found such a simple way to go outside of the game world, and end up on top of the level.
Once I passed through the gate in the Black Garden mission, there's a very distinct and not hidden hole in your walls on the right hand side. I was able to jump my way on ledges around and to the top of the world.
Preeeeetty sure you didn't intend for us to do that...
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They should leave it open and put a dead ghost hiden somewhere