My initial idea is for you to create a Class called something like ‘Grid Tile’, this will contain all the functionality for Spawning a ‘Wall’ or ‘Floor Trap’ at it’s location. You can then create some logic in your Game Mode blueprint that spawns this tile in grids. Spawning in Grids is a case of using a ForLoop to Spawn the ‘Grid Tile BP’ actor’s. You have the ForLoop spawn actors along the X axis Row (for example), then when that is complete, have it run again only starting at the the 2nd Row’s locations. As for saving, it’s a case of creating a Save Class, populating it with variables to store the appropriate data in (Grid Tile state) and then passing that data in however you like.