| Aka: | Sonic blue sphere, Sonic the Hedgehog in Blue Sphere |
| Console: | Sega Genesis |
| TV Standard: | NTSC |
| Country: | United States of America |
| Developer(s): | Sonic Team |
| Publisher(s): | Sega |
| Release Date: | 1994-10-18 |
| Players: | 1 |
| Co-op: | No |
| ESRB: | E - Everyone |
| Type: | Action, Platform |
Blue Sphere, known as Special Stage Mode in Sonic & Knuckles Collection, is an easter egg video game in the Sonic the Hedgehog franchise, built into the Sonic & Knuckles cartridge for the Sega Mega Drive, accessible by attaching any Mega Drive game cartridge (other than Sonic the Hedgehog 2, Sonic the Hedgehog 3 or Sonic & Knuckles) into the Sonic & Knuckles lock-on port. Blue Sphere is a collection of Special Stages in the same style and engine of those featured in Sonic the Hedgehog 3 and Sonic & Knuckles.
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