Got it going :D Interesting mechanic, although it felt inconsistent. Some places it refused to do the 'slap', The hand just disappears when I release. It also seemed possible to 'grapple' by hitting space at the right moment, but this too only seemed to work sometimes. And since it usually left me lodged in an object I wasn't sure if this was a bug or feature XD
I appreciated the visuals. Much of it obviously incomplete, but still more interesting to look at then boxes :D