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Next time don't make two topics about the same thing. But you can use the collision event. Choose the object you want to collide with and any drag and drop actions assigned to that event will trigger then the two objects collide.
Sorry about that. That's my teenage son. I'm trying to teach him game development and a big part of it is figuring out how to research and ask questions well. He still has a lot to learn on this front. Let me clarify for him. He's trying to make the walls of his level have collision. He's followed that top-down bullet hell tutorial that's out there, but it doesn't cover collision. I'm not sure if your answer can apply to room tiles. Thanks for any help you can provide!