This Maplet plots a surface given by a function of two variables, together with a level curve at height z. A 2D plot of the level curve appears below the surface plot. The height of the level curve may be adjusted using the yellow slider to the left of the plot.To adjust the x and y range of the graph, change the values on the right hand side of the Maplet that say "x domain" and "y domain" The zoom factor lets you quickly zoom in and out of the selected view. Slider bars on the plot window adjust the viewing angle. Sliders may be moved with the mouse or changed incrementally by selecting with the mouse and then using the arrow keys. Various buttons on the menu bar change the appearance of the plot.