Firing your cannon is completely mouse based and works by clicking in the "aim" graphic at the top, where angle and power is calculated based on where you click the mouse.

The terrain is made out of a series of colored div elements and image elements with slope graphics. The images are stretched vertically to provide different slopes and elevations. An animated GIF takes care of the explosion effects. Like some of his other games, Scorched Earth uses Nederlof's own old Beehive I library.