Most anime are adapted from manga, but that's far from the only source. Some of the most exciting anime around are adapted from video games.
Many of these anime are based on mobile games. Princess Connect! Re:Dive, a cute story about a guild trying to help one of its members recover his lost memories, started out that way. Others, like CLANNAD and Steins;Gate, are based on visual novels - video games that focus on telling a story. Pokémon, the beloved childhood classic, is based on a game for an early Nintendo handheld console. Cyberpunk: Edgerunners is an animated take on a game that made its way to several consoles and to the computer.
No matter how these games are played, they make for some fantastic anime.