Having read his grandfather's diary which revealed the existence of a top secret military weapon he had invented, Dr. Eggman went to Iron Gate in order to retrieve the weapon and use it for himself in order to conquer the world. When Eggman blows into the Iron Gate on Prison Island, the security systems try to block him off by closing all the metal security doors, forcing Eggman to destroy in order to pass through.
At the bottom of Iron Gate, Dr. Eggman finally succeeds in penetrating the base and finds grandfather's project, codenamed Project Shadow. To his surprise, however, the weapon is revealed to be a hedgehog named Shadow the Hedgehog.
Throughout the level, the security system will alert enemies to Dr. Eggman's presence by announcing the level he is on. The security of the level gets tougher depending on the security level Eggman is on. Most of the time, the player must try to shoot locks off doors or destroy enemies while on moving platforms.
Level Up Item
Eggman's Laser Blaster is located here, but cannot be reached until the player get the Large Blaster Level Up Item from the level Weapons Bed.
Collect 100 Rings
As long as the player does not get hit, collecting one hundred Rings in this stage is fairly easy. To so in under one minute and thirty-five seconds, however, it requires the player to take a detour when they reach the room with the first level-three doors. Upon entering, the player should walk straight ahead, and they should see a large pipe with a spring at the end. They should use it to bounce up onto a platform to the left, then destroy the Iron Container to reveal another spring. The player must then bounce off this Spring and hover to a platform on the right. The player will find ten Rings and three Springs which will bounce them up to a pipe above, where there is a row of rings the player can hover through before dropping back down and continuing on.
Find the lost Chao
The Mystic Melody, large Cannon and Jet Engine Level Up Items are required for this mission. To find the Chao, the same detour that is described in the "Collect 100 Rings" section must be taken, but the player should drop down next to the Ancient Shrine instead of back onto the main path. They must play the Mystic Melody near the shrine to cause a series of platforms to appear which lead to a pulley. The player should ride it into the room above and head around the corner to the right. This will take them to a dead-end where another Ancient Ruin lies. They must play the Mystic Melody again, and a spring and some more platforms appear. The player can find the Chao on the other side of the platforms at the top level against the center of the wall.
Reach the goal within 4:00
This mission is very easy. The player simply needs to continuously fire and try to destroy the doors before they reach them.
Clear Hard mode
The only significant differences here are the addition of more aggressive enemies and the disappearance of quite a few Rings.
Chao Container locations
In the room following the first point marker, the player should take the lift on their right to reach the ledge where the first Chao Container is.
In the Level 3 area of the stage amongst the wooden containers in a side ledge, the second Chao Container is located just before the third Point Marker and Level 4 door.
The third Chao Container is located in the room where the Goal Ring is.