Steam Slug is videogame set in an alternate version of the 19th century. In this game, machines controlled by an unknown entity have risen and waged war on mankind. The sky is already black because of the smoke and destruction the fighting has caused. The machines roam the land and the humans are slowly losing the war against the machines. To turn the tide, the people must fight back and find out who is behind the machines' havoc.
Steam Slug is a third-person shooting game. The game features a steampunk motif. This means that it is set in an industrial environment with machines made from materials such as iron and wood, with these machines’ engines powered by such sources as steam and fire. Realistic physics is applied to the action in the gameplay. For example, enemies shot will crumple and fall based on where they are hit and how strong the ammo used is. Many of the in-game objects can be interacted with. For example, they can be broken, destroyed, or moved. There are also boss fights. In these battles, the player fights an enemy relatively stronger than those enemies that can be battled in that specific level. In the game interface, the player's life can be seen at the upper left portion of the interface.