Clifford

Clifford attractor (Clifford Pickover) — a trigonometric map with no physical derivation, kept because of what it draws. Every parameter change reshapes it entirely, which makes the four knobs worth turning slowly.

x' = sin(a·y) + c·cos(a·x)
y' = sin(b·x) + d·cos(b·y)

It opens running, on the model selector, with its own knobs. Rotate it by dragging, zoom with the wheel, and turn the parameters to see what the figure does when the system changes.