Based on the original game, Super Crate Box I decided to create Mega Crate Box. The idea is to get the maximum number of crates while climbing the scenario while enemies try to kill us.
It is done in Python with the library arcade. I create my own engine based on Unity concepts.
Right now the system has Entities, each entity has Behaviours and can have Colliders.
This structures makes the on_draw and on_update methods really easy to manage.
In fact there is no need to change that loop. You can just add items to the scene.