Systems where there are two linked attributes, and change in either attribute induces change in the other, are really interesting.
I'm specifically thinking of air masses here— if air gets hotter, then it expands and induces less pressure on its surroundings. Conversely, if air has more pressure induced upon it by its surroundings, it's going to get hotter. And correspondingly temperature drops cause contraction and expansion causes temperature increasing.
This sort of system in which two attributes have a deep interplay with each other is pretty interesting. If there's a change in one, it'll change the other, and then because of that other things might happen to change the first one, causing a cycle of changes of states.
Dynamical systems are pretty interesting, and I don't have a lot of deeper understanding of them from a mathematical perspective— so I might mess around with a feedback system like this in @SnepGem's (still work-in-progress with a fractal-visual drawing feature in the works!) L Toy tomorrow.