A fair number of systems created here haven't grokked the behavior of (-), leading to models that don't actually behave as intended. I admit, it took me a few tries to notice, myself. The description given for relationships doesn't help, suggesting that (-) does nothing more than changing 🡩 to 🡫. Having three options, more (🡩), less (🡫), and flip (↕) would have been clearer and more versatile.