Under the Bed
you are the monster. move only in the dark.
be the monster under the bed: sneak a sock, a teddy and the cookies back under it while a kid sweeps the room with a torch. Freeze in the light and you are just laundry.
The kid only sees things that move. Slide the monster while the torch is pointed away, freeze when it swings back, and use the furniture's shadows. Get seen moving and the night is lost. Four nights, each a little harder.
Concepts: perception, attention, motion.
An interactive you play with one thumb, on Wundr.