assuming that the floor use the z axis for instance the object for place an object that block anything on it you need to set the z axys of the floor to 0 and set the z axis of any type of object included the character to 1, obwiusly in any object intended as non walkable surface you need to enable the correct option into its option panel. for stop the character at the end of a floor simlpy add a wall on each edge (if yo don’t want to see the wall in game simply set it invisible in game)