|Number of acts||
In the game's opening cutscene, Shadow finds himself on the outskirts of Westopolis, wondering about just who he is. It is from here that the hedgehog watches with mild disinterest as the Black Arms' crimson clouds swirl over the city, disgorging alien legions into the heart of the metropolis. However, Doom's Eye swims over to meet the Ultimate Lifeform, and an apparition of Black Doom commands Shadow to gather the Chaos Emeralds "as promised" before flitting away. While he's not interested in following orders, Shadow reasons that whether he likes it or not, if Black Doom has knowledge about his past, then he needs to collect the Emeralds and put the alien to the question.
Shortly after arriving in the city, Shadow runs into the one and only Sonic the Hedgehog, who wants Shadow to help him "show the black creatures that we mean business" by repulsing the invaders. Conversely, after Shadow grabs the first (green) Chaos Emerald, Doom's Eye approaches (commenting that he is "late"), and sets him with the task of destroying the GUN soldiers. It is up to the player to decide who to help; or to take the neutral route and just go straight for the second Emerald.
Westopolis is still under heavy bombardment as the Black Arms troops war against G.U.N. soldiers, while the Black Comet showers the city with orbital lasers impacts, as Shadow fights his way through the streets. Half-destroyed roads, buildings, and burning car wreckage litter the stage, and some buildings can even be seen toppling over during the stage. The "Red Fruits", as they are called in-game, are found in small clusters at various points in the stage. There are some metal bridge like structures that are knocked down by the lasers that can provide alternative routes through the level. There are even some damaged buses that can be flipped over to crush foes, as well as speed limit signs that can be knocked down and subsequently used for bashing heads. As for the state of the city, the soldiers will sometimes comment that "the entire city is on fire!" during the stage. In later cutscenes, a soldier informs the G.U.N. Commander that the city of the United Federation connected up by Lethal Highway, is one of six urban centers hit by the Black Arms right at the start of their invasion of Sonic's world, and has received the heaviest casualties, due to weakened defenses, and that "downtown Westopolis is almost completely destroyed."
Annihilate the GUN forces!
- Guide: Doom's Eye
- Objective: Defeat all 35 GUN enemies in Westopolis.
- Tips: 10 GUN enemies should have been defeated by the time you reach checkpoint #2, 20 by checkpoint #3, 26 by checkpoint #4, 33 before checkpoint #5, and all 35 before the final checkpoint.
- Make sure to get GUN enemies lying on the ground.
|A||≥ 30,000 points|
|E||< 5000 points|
Leads to: Digital Circuit
Find the Chaos Emerald!
- Objective: Reach the Goal Ring.
- Tips: The goal ring is right after checkpoint #5.
|A||≥ 32,000 points|
|E||> 10,000 points|
Leads to: Glyphic Canyon
Drive off the black creatures!
- Guide: Sonic
- Objective: Defeat all 45 Black Arms in Westopolis.
- Tips: 23 Black Arms should have been defeated by the time you reach checkpoint #2, 29 by checkpoint #3, 33 by checkpoint #4, 42 before checkpoint #5, and all 45 before the final checkpoint.
|A||≥ 30,000 points|
|E||< 5000 points|
Leads to: Lethal Highway
Behind the Secret DoorEdit
A gun with 20 shots, and an Armored Car.
- To complete the game 100%, the player will need to play this level 326 times.
- In Expert Mode, Doctor Eggman wishes Shadow good luck via a hint marker.
- This is the first game in the series to feature Sky Diving done at the beginning of the stage and at the very end past the Goal Ring in normal mode and before it in Expert Mode.
- If one were to play with Sonic with 2nd controller not only does he Homing Attack Black Arms, but can also hurt G.U.N soldiers with it. He seems to function more like Shadow than other hero characters; he can activate switches, put out fires, open locked key doors, and he even has a scripted Sky Diving sequence which can be done at the end of the level.
- Strangely while running at full speed with Sonic and then pull the control stick down to brake to a halt he shares the same hovershoe SFX as Shadow when he brakes.
- No matter what mission you do, the Commander will think Shadow is working for the Black Arms.
- The hint bubble where Sonic suggests to Shadow that they use the homing attack on GUN beetles to cross a gap was originally supposed to have Sonic use the word "piss" (ie, "Hate to piss off GUN..."), but it was changed to "tick" in the final version.