Let the round ghosts drop off the screen by changing their color. When they're green, they'll fall through green blocks and when they're lilac, they'll fall through lilac blocks. So the trick is to drop them in the right order and at the right moment. Don't hit humans and don't make humans disappear from the screen. This game seems really simple, but it takes more brainwork than you expect!
Click on the ghosts to make them change color.