I have an obj assigned as an overlay to another obj (this was necesary in order to assign a pixel_y value to the overlay obj, for cards that span 2 tiles). When I change the icon_state of the overlay obj, it doesn't seem to take effect unless I remove and re-add the overlay:

resource.overlays -= resource.top_half
resource.overlays += resource.top_half

It seems like there must be a better way to handle this, though I didn't see anything under overlays on the DM help. Any suggestions?