The Van der Pol oscillator

With μ above 0, click anywhere to release an orbit from that point: from inside the loop it is pushed out, from outside it is pulled in, and either way it lands on the gold loop (at μ = 0 every orbit keeps circling on its own). Drag μ up and the motion on the loop splits in two, a slow crawl along the horizontal axis and then a sudden fling to the other side. The corner shows x(t) for your orbit: the crawls are the flat stretches of the square wave, the flings its steep edges.