A genre of video game in which the characters exist on a 2D plane (or mostly 2D plane), and they run side to side, often with the ability to jump up or down to different points on the map to avoid obstacles or reach objectives. As the player runs to one side of the screen, the camera will follow them, allowing them to uncover more of the map as they go.
"Oh, is that another one of those side-scroller games?"

"Huh? Oh, yeah... I've just been running right forever. I think it's endless."
by RandomPhail August 27, 2018