This simulator models the motions of the sun in the sky using a horizon diagram, demonstrating daily and seasonal changes in the sun's position.
The upper left panel shows the horizon diagram visualization. This is a representation of the sky as if it were a large sphere centered on an observer (the stickfigure). The location and local time for this observer are set in the Time and Location Controls panel.
The General Settings panel allows one to show or hide various features of the horizon diagram, as well as controlling the behavior when dragging the sun disk on the horizon diagram.
When animating, this simulator can run continuously (as if in fast forward) or it can step by day. Stepping by day keeps the time of day fixed as the day of year changes. For example, one can use this mode to see the path the noon time sun traces over the year.