This interactive shadow simulation demonstrates how a light source, such as the sun, casts shadows on a flat, circular Earth model. By adjusting the latitude and longitude of the light source, users can observe the resulting shadow lengths and directions at different locations around the map. The simulation allows the positions of two rods and a gnomon to be set freely, both manually and by dragging them with the mouse. As the virtual sun moves, the shadows change in real time, illustrating the relationship between observer position, sun angle, and shadow geometry. Users can also animate the sun’s path or examine specific dates by controlling its speed and latitude. An additional graph feature visualizes how shadow length varies with longitude for each rod and the gnomon. This tool provides an intuitive way to explore sunlight, seasons, and the geometry of shadows on a circular Earth projection.