I looked into the code a bit (was so long since I did this project I've forgotten how it works :P). The panels used for movement actually are objects, that's probably since it's mouse-controlled and I wanted an easy way to let you click on them. Enemies use them too, they're just deleting them right afterwards so they're not shown to the player. I do use queues and priority queues to order stuff, though, so if you absolutely don't wanna touch data structures this is a bit of a no go.