Serious Sam Double D is a 2011 side-scrolling shooter game developed by Mommy's Best Games and published by Devolver Digital. The game follows Sam "Serious" Stone traveling through various historical settings to destroy the horde of his nemesis, Mental, and its teleportation beacons. As Sam, the player navigates 2D levels and can use the "gun stacker" to create vertical stacks of up to six weapons that are fired simultaneously.