Kitten play is centered around predatory-like behavior. Kittens learn the specifics how to be cats mostly by imitation of their mother and other cats (and will, for example, prefer the prey their mother trained them on or start stalking a new prey animal after seeing another cat catch one—although they don’t actually need to be trained in order to become good predators). A cat will not usually attack prey while on its back, with its prey object on its tummy, but this kitten is improving its paw-eye coordination, and ‘hugging’ its target, and, apparently, imitating its … you know … next best thing to mom.
Oh, and did I mention it’s also the cutest thing in the universe?
[this is good]