"Get Blue Spheres!"
When Sonic the Hedgehog was tasked with collecting the Chaos Emeralds in Sonic the Hedgehog 3 he had to enter a pseudo-3D bonus round filled with blue, red, yellow, and white-stared spheres. By running over the surface of a massive sphere he had to run over all the blue sphere and collecting the rings they left behind. Whenever a blue sphere is touched it becomes a red sphere, and touching a red sphere ends the bonus round. This bonus round is called Blue Sphere.
Sonic the Hedgehog 3 featured seven distinct Blue Sphere levels which traditionally began at an easy level and became more and more difficult as time went by, requiring Sonic to collect more and more blue spheres that were set in the middle of a sea of red ones. Touching a yellow sphere causes Sonic to be sprung ahead a good distance, while bumping into a white sphere with a red star on it causes him to shift into reverse direction. Sonic can jump over spheres he doesn't want to touch, but the trick to these levels is that he cannot stop. Running over blue spheres in such as manner as to create a ring of red spheres around remaining blue ones (a square, basically) results in all the spheres in that formation turning into rings. Furthermore, the longer Sonic spends in each level the faster he runs causing the player to react faster as time ticks by. Tails can also enter Blue Sphere if the player is playing as him. The combination of Sonic and Tails can also play, but the CPU controls Tails. He follows directly behind Sonic, but if he touched a red sphere then the round ends. Note tha Tails can not fly in Blue Sphere like he can during normal levels.
Blue Sphere returned in Sonic and Knuckles with seven all new arrangements of spheres. These levels picked up in difficulty where Sonic 3's left off, plus now Knuckles (being a playable character) could access them. Note that Knuckles can not glide during Blue Sphere like he can during normal levels. When the game is locked-on to Sonic 3 to become Sonic 3 and Knuckles all fourteen Blue Sphere rounds become available and are randomly distributed among the fourteen needed emeralds.
Fans of the bonus round can lock their Sonic and Knuckles cartridge onto the original Sega Genesis Sonic the Hedgehog game. Although initially the game will display a "No Way!" message, pressing the A, B, and C buttons at once pulls up a series of all new Blue Sphere levels. The only objective now is to clear the board; there are no Chaos Emeralds to collect and no Dr. Robotnik to stop. The objective is fun and testing reaction time. At the end of each level the game will display a password so that during the next play session gamers can pick up where they left off. You'll need the password if you want to finish the game as there are millions of Blue Sphere rounds to challenge you. Players can alternate between Sonic and Knuckles by pressing a button at the Blue Sphere level screen. If you connect the Sonic and Knuckles cartridge to other games sometimes a single Blue Sphere level will be generated by the cartridge's internal serial code. This does not work on all cartridges, however.
While the game also appears in the PC port The Sonic and Knuckles Collection, Blue Sphere didn't officially get a title until its 2002 appearance in the Sonic Mega Collection for the Nintendo GameCube. When players play Sonic 3D Blast and Dr. Robotnik's Mean Bean Machine twenty times each the game becomes available on the menu screen (The game can also be unlocked if a Phantasy Star Online save file is on your memory card). | 
