I've played this puzzle quite a bit on "Simon Tatham's Portable Puzzle Collection" (which is awesome by the way), and it has one feature that I don't see here. With it, if you have notes on a region (eg yellow and red hashes), you can drag that region to an empty region, and it adds the same notes to that region.
This feature is extremely useful, and it really bothers me that I can't do the same thing here. Could it be added?
This feature is extremely useful, and it really bothers me that I can't do the same thing here. Could it be added?