Simple but entertaining for a bit. The difficulty seems to cap out, though, I got bored a bit over 250 and stopped because it wasn't getting any harder. I feel like it could get a bit tougher.
Also, holding space is a bit odd, since there's never a reason to not hold space. I just held down space with my other hand the entire time, which made it feel like it might as well not be a feature. If you wanted to keep it, you could make it so that you can't move while you're holding space, which makes it much tricker and ensures the player has to press space only when they need to and not just all the time.