I liked the idea of splitting the game between a 3D world and a 2D world. The idea for having two levels you can switch between is also quite cool, but I feel like the two levels could "interact" with each other more. Good job, especially considering you were a one person team!
There were some bugs, but that it to be more or less expected from a game made in a week. At one point I glitched out of the 2D world and there was no way to restart the level, which was quite annoying. Also the fact that dying restarts your whole game instead of just your progress in the 2D world was frustrating.
The controls could be improved a bit - jumping could have been slightly better and the shooting felt a bit unintuitive at first - considering that you use your mouse to shoot I expected to be able to shoot in the direction of my cursor, not in the direction I was looking, but other than that it felt satysfying