Very cool concept with an amazing amount of content included. I understand people saying they don't think it fits the theme and saying they've seen it before, but I think the application of it with this type of game is uniques and ties it in.
The graphics are great and the sound effects are pretty good. I think the camera can make things a little difficult when you rotate the cube.
I also noticed a lot of issues with the bullets teleporting around when the cube was rotating, and I had issues with weird physics with dead towers when the cube was rotating. Sometimes this ended up throwing me off so much I died.
Also, the bright white auto-exposure when the cube is rotated towards you makes it difficult to see things.
Overall, very cool entry.