The whole tradition of 'corrupted childhood' is a classic horror staple, as seen in movies like The Omen. And this takes that harmless play of children in a playground and makes it dark and creepy, and it works.
Good job.
If you ever want some stuff for future projects check here, I will be adding a horror pack down the road but even now tons of textures, 3d files so any game devs watching may want to give it a look.