You should be able to move, at least i am able to move. the thing is the fins unlocks your movements. so in the start you have one fin from the back which thrusts you forwards. if you get one to your left that unlocks the D button which will thrust you to the right.
i have failed comunicating this but im not really sure how to do so without a tutorial or a wall of text in the beginning.
i was hoping the fact that all you see at the start is W and when a fin appears you see the other buttons would be enough to communicate that element of the game. but im guessing thats where the confusion lies
thanks for your comment!