KetoprakDL – Sonic Rivals is a racing video game, part of the Sonic the Hedgehog series that was released in late 2006. It is the first Sonic game developed by Backbone Entertainment, for the PlayStation Portable. The game was also supervised by members of Sega Studio USA including Takashi Iizuka.
One year later, a sequel was developed by the same company for the same platform.
Sonic Rivals is a side-scrolling video game similar to the original Sonic the Hedgehog games for the Sega Genesis, but with a 2.5D perspective. Characters race to the finish line while avoiding the level’s obstacles. The game contains six zones, each with three respective acts, the third being a boss battle, totaling in 17 stages. Boss battles at the end of levels require the player to defeat the boss before the competing character does. Five different characters are playable; Sonic the Hedgehog, Knuckles the Echidna, Shadow the Hedgehog, Silver the Hedgehog, and Metal Sonic, but gameplay is identical for all characters. The game features power-ups to collect that offer additional offensive and defensive abilities.
Source : Wikipedia