AxelDeathBR

Hello, I'm a newbie, I'm creating a game, actually studying the engine to learn, I tried everything but the monsters go up and don't come back when they collide, when there is no collision they go up infinitely until they stop at the end of the map, I don't quite understand how this works, it's in random mode, shouldn't there be something to configure this? image:

Salve meu mano.