Crystal Egg Zone
From Sonic Retro
Crystal Egg Zone, the eight zone in Sonic the Hedgehog 2 (Game Gear), has weird bright colours mask the hardest stage in the game. The boss is is a different story altogether, at is almost entirely black. A bunch of spikes make an appearence here as expected, and it is a very suitable last level. You can only get here with all emeralds, else the game ends after beating Silver Sonic.