Sonic the Hedgehog 4 (originally titled "Project Needlemouse") is an episodic WiiWare game starring Sonic the Hedgehog. It is meant to be a direct sequel to Sonic the Hedgehog 3 and Sonic & Knuckles, and incorporates motion controls.
Episode 1 was released for WiiWare in North America on October 11, 2010, in Japan on October 12, 2010 and in the PAL region on October 15, 2010. There are no plans to release any additional episodes for this console, as SEGA's digital brand manager Ken Balough wrote the following statement:
"But no - the reason Episode I was on the Wii was because we wanted to bring the Sonic 4 saga to the widest possible audience. Episode II unfortunately will not be coming to the Wii - for reasons most people have probably guessed, but that doesn't mean the SEGA isn't supporting Nintendo platforms, we have a very strong partnership and will continue to do so."
After destroying the Death Egg, Sonic decides to take a break from saving the world and explore new places. Unbeknownst to him, though, Dr. Eggman is still alive and is setting a trap to get rid of Sonic.
If you get all the Chaos Emeralds in Episode 1 you will see a preview of Episode 2, which will only be released for the Xbox 360 & Playstation 3 consoles.
Sonic the Hedgehog 4 is a side-scrolling platformer, just like the original Sonic games, and includes levels reminiscent of the older Sonic games.