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Simple, fast-paced games with colorful graphics and catchy audio, that require few or no explanations, can be played in short bursts, and usually require a lot of skill. Similar in style and spirit with the arcade game cabinets of the 80s and 90s.

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

The larger universe outside of Earth's atmosphere. Sometimes really, really far outside of it.

A perspective where the camera is placed directly above the player. Common in 2D games, but can also be used in 3D games.