This is a nice, short game you made. I guess it would get a bit repetetive after a while, but you could always add more things to make it more interesting. As others mentioned, there could be something at the end of a level to tell you to press space, for example a flickering text or something. There should also be something like names of the levels at the start of each, so the player has more visual feedback. But overall this game is pretty good.