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Typically refers to a style of game where a player's ship can rotate 360 degrees on a 2d plane and is responsible for shooting and destroying on coming asteroids. The asteroids start out large, but divide into smaller obstacles as they are damaged. The game becomes more difficult and chaotic as asteroids are broken into the smaller pieces.

Science-fiction. Commonly including things like aliens, advanced technology, and settings of outer space or distant planets. 

Games which have short playtimes and can usually be completed in one sitting.