Longest-running open-source beat-'em-up videogame engine

Although Senile Team's Beats of Rage (Senile Team, 2003) has since been officially discontinued, its ability to allow gamers to create their own side-scrolling beat-'em-up titles without the need for any programming experience has kept the 2D game engine alive as an open-source project. Indeed, having been designed as a tribute to Streets of Rage and ported to numerous machines including the PlayStation 2, PSP, Dreamcast and Xbox, it now lives on as the OpenBOR project with dozens of videogames continuing to be made using it. As well as beat-'em-ups, games in other genres such as platformers and RPGs have been created using this facility.