Ooh shit i love this! thats so smart and unique! first it seems like a brief air of "this is a short platformer nothing much" and then as you advance you realize the simple but amazingly unique game mechanics! YOU are the tower and your shots could be elevated or depression of the floor of the tower that shoots! And also the pedagoic progressive instructions of how to play is perfectly coherent. The only think i could wish for is some suitable music.
Well done!