As others have said, not the most fun I've had of a Saturday morning. I think I've struggled to the end but I can only see 9 themes. Is there one that's less obviously a themed answer? Don't want to give spoilers, but I have 3 in the NW, 2 in the NE, 3 in the SE and 1 in the SW. Also not sure of the parsing of 16 down.