the GameScene no longer needs to keep track of the "pipes". It's the World's responsiblity how it handles itself when it needs to be "reset". There are just pipes now that need removing, but perhaps in the future there will be butterflies or trees. The World will create the trees/butterflies, and it will also know how and what to remove in its "resetWorld" method. It's the World's responsbility, not the GameScene's