A lot of nice work, with just a couple of things of polish and bugs to improve things for next time.
I wasn't sure what the power ups were for, but it was the only sound to work in the game.
I didn't know or notice the change element until the end, but I never needed to, the ship firing was fine for everything. Needed to mix in a challenge to make me want to change, and to make it more obvious.
Bit relative in the cycle to, needed a difficulty ramp and extra levels.
However, I know what time constraints can be like in game jams. So most of these points may well have just been out of scope for you in the time you had, so great job on putting it together in a week! Well done!