just an fyi, I'm not saying that you have to make huge layouts with lots of interconnecting areas, but if you have a need for sectioning off parts of your level then this is one way to do it. Castlevania games have single-screen rooms and short connecting hallways all the time, the method I posted is just fine for making those kinds of things.
Parts of levels are sectioned off in other games like Mega Man, Metroid, etc. In fact, I would say this method is probably perfect for Mega Man type scrolling, you would just have to add in some auto-scroll events to transition to the next room. And I really don't think it would be more efficient to have each little section of, for example, a Mega Man level (but also to some extent Castlevania as well) in it's own layout.
As for resetting enemies, make some enemy spawner objects in your level and spawn them when you walk into a new section and destroy them when you leave, or... oh hell, just do whatever you want. I don't care, why am I even trying to defend this?
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