Okay I found out from another forum what it's about. Hang on I'll get the info now...
Set in Arthurian legend, the game combines Sonic's trademark speed with a new swordfighting system, making use of the Wii Remote's motion-sensing functionality.
A sorceress named Merlina summons Sonic to help free the mystical realm of King Arthur, where King Arthur has been corrupted and is now ruling the realm as the tyrannical Black Knight. Sonic's speed alone will not end Arthur's reign, so he must take up the sword in order to save the kingdom.
Gameplay for Sonic and the Black Knight differs from traditional games in the Sonic series by mixing in the new element of swordplay, along with the traditional Sonic platforming and speed. Swordplay is implemented through the Wii Remote and hence, unlike Sonic and the Secret Rings, players will now control Sonic's movement with the analog stick. The gameplay will mainly be 3D, but occasionally the camera will shift to a side-scrolling perspective for traditional 2D gameplay.
Swordplay will be implemented so that players can slice through enemies without slowing down, but when faced with more formidable enemies, players will engage in advanced swordsplay, able to thrust, parry, and even perform a buzz-saw manuever mid-jump. The sword will not be only used for combat; players may thrust it through a wall while falling to slow their decent.
The stages will feature civilians that the player can choose to help or smite; these actions and the player's deeds will be judged at the end of each stage, updating the player's knight ranking accordingly. By helping out grateful citizens, players will be able to purchase new items from them, acquiring items such as gauntlets, magical tomes, and new swords. There will be about two hundred items in the game, some of which can be gained by opening treasure chests in the stages. An online mode will allow treasures to be traded.
The game changes the traditional level items, such as springs and speed pads, into elements. These elements look similar to Chao heads, and come in different colours; red elements will be used as springs, yellow elements will be used as speed boosts, and purple elements will be used to fill up the special gauge. This gauge, replacing the previous entry's soul gauge, is filled by defeating enemies, and is used to unleash a powerful combination attack. In additional, traditional rails will not feature, and so to traverse between points, players will fire a ballista and then grind across its rope.
The mission based system from the Sonic and the Secret Rings will also return, but will be made less arduous; each stage will consist of multiple missions which feature different stipulations. The skill system from the aforementioned game also returns, but will be reviewed to adjust any problems that were present in that game; the skill system is also being designed so as not to interfere with the game's tempo.