This demo shows a level set consisting of level curves `f(x,y) = c` for the Twin Peaks function `f(x,y) = 3(-x`^{4} + x^{2} - y^{2}). A contour map is drawn in the window labeled "Domain: f(x,y)". The third window, labeled "Level Curves", allows you to choose a level curve `f(x,y) = h` by dragging the hotspot along the `z`-axis. The value of the constant `h` is shown in the control panel.