Thank you for playing it. I'm glad you liked it!
In godot 4.5, I used a Tilemaplayer with a tilemap with navigation layer enabled and navigation polygons painted on the tiles that are walkable. NPCs have navigationagent2d nodes for pathfinding. here are some links I found useful:
https://docs.godotengine.org/en/4.5/tutorials/navigation/navigation_using_naviga...