Open Sonic written by Alexandre Martins for AmigaOS4 is an open-source game based on the “Sonic the Hedgehog” universe. It introduces a different style of gameplay called cooperative play, in which it’s possible to control 3 characters simultaneously. Unlike most similar games, Open Sonic provides a greater level of interaction between the player and the levels. It’s more than just a jump’n’run; the user must come up with some strategy in order to get through the levels. Sonic’s first major appearance was in the platform game Sonic the Hedgehog for the Sega Mega Drive/Genesis in 1991, which also introduced his nemesis Dr. Robotnik. His two-tailed fox friend Tails joined him in the game’s 1992 sequel.