Moon Zone
Collect all Chaos Emeralds by the end of the game, then play Sonic's X-zone. Successfully complete the zone to unlock the bonus Moon zone.

Fly Off Screen
Play as Sonic (recommended), Miles, or Knuckles. Go to Zone 1 Act 1 and go to the area where the first loop is located. Stand on the sliver of land, then charge a spin dash for 20 seconds. Dash to the right and hold Down/Right. You will go down the hill (not getting all the rings). Eventually, you will go so fast that you will leave the screen. Sometimes it does not launch you off the cliff at the end.

%100 Armor
Press #86642# during game play.

Mines Part 1: Secret Room 1
Go through the level and collect the Remote Mines. Once you witness the "Ultor Guard", kill the miner, go over to him, and kill him. After you kill him, go right instead of left. There is another guard watching over some health and ammunition.

Mines Part 1: Secret Room 2
Go through the level until you reach the first wall to your right that says "FOS Rules". Toss a Remote Mine near it and back up. Press the switch to explode the mine. It will open up a passage with lots of health in it.

Mines Part 1: Get Automatic Shotgun Early
Go through the level and collect the Remote Mines, as you will need them later. Continue until you reach a point where there are two yellow cases on the right being watched by two guards. Take out the guards, then toss a Remote Mine near the two cases. It will explode, opening a passage. Go right and collect the health, then go back to the entrance of the hidden passage and go left to collect the Automatic Shotgun. It is a very useful weapon because it kills regular guards in one hit and the yellow guards in two or three hits.

Big Hammer

In the first level, go up the first hill you come to, then if you jump off at the correct angle, you will do a very high jump! As you fall back down to the ground, press R/L simutanously. At the same time press AYBXXBYA. This will make you do another jump in mid-air! You can jump up, and if done correctly,you will see a hammer floating in mid-air. You will land on it. Now you can smash enemies by pressing R!