Game replay file, or "demo," created by Hedgewars, a turn-based game similar to the Worms series, but uses hedgehogs instead of worms; saves a replay of a map played by the user; allows users to review previously played games.

After completing a map, Hedgewars asks if you would like to save a demo. If you choose "yes," Hedgewars creates an HWD file that can be used for replay or for sharing with other Hedgewars players.