The mech missions are of average difficulty, and feature a variety of energy-based or explosive projectile weapons. Much of the action takes place within city areas.
The on-foot missions feature a variety of mostly hitscan firearms, such as dual pistols, an Uzi-like machine gun, and an assault rifle (non-hitscan weapons include two types of grenade launchers and a TOW rocket launcher). These sections of the game are quite difficult; your character (Sanjuro) cannot survive much damage, enemies are equipped with rapid-fire hit-scan weapons and have great aim, health items are somewhat scarce, and armor is extremely rare.
Shogo also has an interesting gameplay feature in its critical hits system, whereby attacking an enemy will occasionally bring about a health bonus for the player while the enemy in question loses more health than usual from the weapon used. However, enemy characters are also capable of scoring critical hits on the player. It should also be noted that each of the weapons in the game have different likelihoods of scoring critical hits on an enemy.
At two pivotal points in the game, the player also has the opportunity to make a crucial decision, which can alter the game's ending. While the first decision is almost purely a narrative decision, the second decision actually determines who you'll be facing the rest of the game and how the game will end. If nothing else, the ability to play the game twice with two different sets of final missions truly added to the title's replay value.
The game begins with Sanjuro being extracted from a reconnaissance mission two years after the mission against Ivan Isarevich that resulted in Kura, Toshiro, and Baku's supposed deaths. He is brought to the Leviathan, a UCA command ship, and receives his mission from Admiral Akkaraju, who is Kura and Kathryn's father. Sanjuro then is dropped onto the planet to enter the city of Avernus and kill Gabriel, leader of the Fallen. Once Sanjuro reaches Avernus, a mysterious man called Hank Johnson, a "friend of a friend," warns him about reinforcements coming in. Sanjuro attempts to reach Gabriel's headquarters. But it's a trap: communications with the Leviathan are jammed by an interference array, and Uziel, Gabriel's right-hand man, blocks Sanjuro's way after claiming that he knows him. Sanjuro, assisted by Hank, reaches the base with the interference array, and assists a UCA unit, Strike Force Carnivore against the enemy. He deactivates the array and establishes contact, but hears Kura instead of Kathryn. It is revealed that Kura was not dead, and she asks to meet with Sanjuro in Maritropa, a nearby city on Cronus to explain everything. Admiral Akkaraju, however, dodges the question of why he didn't tell Sanjuro about this, and orders Sanjuro to withdraw. Sanjuro then exits through the sewer to avoid the reinforcements; in the process of doing so, he learns that the soldiers have overwhelmed Strike Force Carnivore, and have secured his MCA. Reaching a parking garage he passed through earlier, Sanjuro kills some soldiers and destroys a tank, allowing Hank to help him escape in the back of his truck.
Hank takes Sanjuro to a pumping station, and with his help, dispatches the guards and helps Sanjuro get another MCA. Despite Kathryn's insistence that Toshiro and Baku are dead, Sanjuro suspects that both are alive, and decides to meet Kura at a nightclub called "The Mecca." With two friends of Hank's, he proceeds through the city and reaches a train station, but is too late to catch the train. Sanjuro then passes through the slums of Maritropa, but an electric gate bars his way, and only a woman whose cat is missing is able to deactivate it. The player can either kill the woman and her husband and open the gate, or do an optional level which depicts Sanjuro's attempts to rescue the cat from some "stragglers" who have been severely affected by working with kato, leading to a humorous exchange between Sanjuro and Kura, and Sanjuro receiving a health powerup as well as the cat's "toy" - a doll of Captain Nathaniel Joseph Claw from Monolith's own platformer Claw, that, when squeezed, says "Commander Claw" (Sanjuro actually gets to keep this item for the rest of the game). Sanjuro reaches the Mecca too late; Kura has been captured by the CMC, Cronus's relatively weak yet troublesome military authority, but not before she says that Toshiro is Gabriel, and vaguely mentions "Cothineal." Sanjuro reaches the club, and a businessman from Shogo named Ryo Ishikawa agrees to help Sanjuro save Kura in exchange for a favor. Sanjuro reluctantly agrees, and makes his way to the station, before moving crosstown in his MCA, and catching another train to the detention center. At the station, Hank tells him that Cothineal "is the reason the Fallen exist," but says that Kura can elaborate.
At the detention center, Ryo asks Sanjuro to deactivate a firewall. The player has another choice here; if he helps Ryo, Ryo will leave him stranded by deactivating an energy walkway, forcing Hank to help him escape. If he does not, Ryo triggers the alarms. In either situation, Sanjuro is forced to shoot his way through the CMC, rescuing Kura, who reveals that she was working undercover, which is why she was listed as dead. Kathryn then informs Sanjuro that the Admiral wants to fire the kato cannon at Avernus despite High Command's insistence, but doesn't know why. Sanjuro, who knows that the blast could affect Maritropa and Constantine, asks Kathryn to delay the admiral until he returns. After defeating the Fallen assassins who are trying to kill Kura, Kura tells Sanjuro that Cothineal is the source of kato, and that Toshiro is acting as a pawn. Baku, meanwhile, has become insane, and as Kura notes, "I don't know what he's become, but he's dangerous." Kura expresses her concern that Admiral Akkaraju considers Toshiro a traitor. Kura then asks Sanjuro to come to the Oshii Research Station in Avernus, which supposedly has proof of Cothineal's existence and role. She then asks Sanjuro about his relationship with Kathryn, but the choice the player makes doesn't have any clear effect other than dialogue.
On the train ride back, an upset Kathryn shares her displeasure with Sanjuro. Ryo Ishikawa then contacts him, and reveals some of his more sinister dealings. He states that he played at least some role in Ivan Isarevich's rise to power, and implies that he has a stake in the current crisis in the excellent quote of "Two years ago, when you and your squad went into Avernus and killed Ivan Isarevich, you did a lot more than liquidate an up and coming tyrant- you wrecked a scheme that I'd nurtured for years. It's taken me a long time to recover from the mess you've made, and now you're trying to ruin me again. Who do you think tipped off the CMC about your little lovebird, anyway?" Ryo then sends the train out of control, and has the Shogo troops on board attack Sanjuro. Sanjuro saves the train, but when he gets back to the pumping station, it is overrun by Shogo troops. He is forced to watch as Ryo shoots Hank in the head with a shotgun blast, execution-style, killing him. Ryo escapes before Sanjuro can reach him. Kathryn expresses condolences, and convinces Sanjuro to go to the airship dock to reach the Oshii Research Station. He finds Uziel's MCA there, and forces him to retreat after a brief skirmish. He then contacts Toshiro, and arranges a meeting in the History of Warfare museum in Avernus. Sanjuro's efforts are nearly stymied when Admiral Akkaraju announces that the Kato cannon is charging and will fire in two hours; he cites evidence by Ryo Ishikawa, whom he sees as an ally, as proof of Toshiro's treachery. He also will not hear anything of Sanjuro's claims that if he fires the kato cannon and disobeys High Command, "The UCA will be thrown into chaos and the Fallen will be out of the way. The CMC is already in tatters- Shogo will inherit Cronus."
Sanjuro reaches the Oshii research station, and he and Kura find the necessary information despite a raid by Shogo troops. The Admiral reluctantly agrees, and gives Sanjuro one last chance to save Toshiro. Sanjuro reaches the History of Warfare museum, and sees Gabriel, who gives the player a choice of joining him or facing his armies.
Sanjuro accepts, and fights UCA troopers before reaching a ship to board the Leviathan. Sanjuro meets up with Kathryn, and fights his way through the ship to reach the kato cannon firing controls. With minutes left to go, Sanjuro disables them, and defeats Ryo, who plans on reactivating the kato cannon, which was most likely his reason for telling the admiral what he did. The epilogue suggests that the Admiral will be court-martialed, the CMC has surrendered, and the Fallen have declared a truce with the UCA and Toshiro remaining on Cronus as an "ambassador" to Cothineal.
Sanjuro refuses, and fights Fallen troopers inside the ruined museum. He escapes and, defeating Fallen troops in the city, proceeds on to the Fallen headquarters using the same way he planned on using early in the game. He proceeds through the city rooftops, and on to the outskirts of the city, where he learns that Shogo fighters are attacking the Leviathan. Sanjuro enters the elevator leading to Gabriel, and, brushing off Kathryn's concerns, fights with and defeats Baku. Sanjuro reaches Gabriel, who is being protected by an energy field that Cothineal creates, and learns that Shogo reinforcements will attack from behind. Sanjuro shoots Cothineal's eye, lowering Gabriel's defenses, and disables Gabriel's MCA. He then defeats Ryo's reinforcements, and Ryo himself. The epilogue notes that Toshiro is being treated for his time under Cothineal's control, and that Admiral Akkaraju will be investigated for disobeying High Command, but little will come of it. Humanity will also work to gain peace with Cothineal.
The expansion pack, Shugotenshi would have given us more insight into Kura's roles. It would have been 6 or 8 levels of Kura fighting and coming to terms with the death of Hank. Some features of that game would have been various body armor for Kura, new enemies and weapons for her to use.
Legacy of the Fallen would have taken us away from the fighting of Cronus and taken us to the remote Kato mining facility at Iota-33. We would see just how well organised the Fallen actually is, and be shown the weapon capabilities of an Ambed (Advanced Mechanical Biological Engineering Division) team. Legacy of the Fallen was to have an entirely new cast of characters, five new mecha to choose from, six new onfoot weapons, five new mecha weapons, several new enemy aliens and levels that played out more like Half-Life's levels in structure. Instead of each level being fully independent, going between levels would have had the player having a small amount of loading with just the word Loading on the screen and then seamlessly being in the next level.
Each mech can transform into a hover-transport mode for high-speed transit (weapons cannot be fired in transport mode). The primary difference between the four is their melee weapon, speed, and number of hit points. The Ordog carries a combat knife and possesses 1,000 HP and up to 2,000 Armor and is the second fastest MCA behind the Akuma but has the worst vehicle-mode handling compared to the other MCAs. The Enforcer carries an energy blade and, like the Ordog, possesses 1,000 HP and up to 2,000 Armor and is noticeably slower but makes up for this by not having the Ordog's maneuverability problems. The Akuma carries a katana and possesses 800 HP and up to 1,600 Armor and is easily the fastest MCA in the game. The heavyweight Predator is by far the slowest and carries an energy baton and possesses 1,200 HP and up to 2,400 Armor. In terms of movement performance and weapons loadout, however, there is little perceptible difference between the various mecha. The games' manual states that one of the items can upgrade the look and performance of your mech (Armor and HP wise). The opening cinematic of the game shows a white mech - hinting the Mark VII Enforcer with upgrades.
There are numerous enemy mecha, but most have lengthy recoil animations from damage that exceed the average reload time of the player's weapons, as a result it is easy to constantly damage the enemy and have them perform the animation until dead and take little or no damage even from many enemies engaged at once.
Monolith has repeatedly stated they have no current intention of doing a sequel, but numerous Shogo themed easter eggs have turned up in their later projects: No One Lives Forever featured Hank Johnson's grave in the game's last level; The Matrix Online features a nightclub called "Club Shogo"; Blood II: The Chosen features Shogo posters in various rooms in the CabalCo building's living quarters; F.E.A.R. has the Armacham company name, the Bullgut (called the MOD-3 Multi-Rocket launcher) and even the Shredder (called the MP-50 Repeating Cannon) as weapons, plus a secret room with a radio that plays the opening theme music from Shogo and uses a Shogo texture depicting a man riding on a horse. Plus there are also textures that depict the Enforcer mecha as belonging to Shogo Industries and a texture depicting the Shogo cover art probably as a poster. Plus some players have said that the UAV in F.E.A.R. looks similar to the Spider Mine in Shogo.
The obvious content that was taken out can be seen in some of the various movies on the official site. The shotgun was originally going to have a shoulder stock that was flipped up and out of the way of the handle. A weapon that was dropped, the pinpunchers, were the mecha equivalent of the two pistols that are the default weapon of on-foot gameplay. The game was to have different static pictures in the background during level change. These pictures would give you a preview of the action of the next level or just give you a glimpse at some of the enemies you would have to fight. There is also a file named leviathan.mov that gives a moving image of the ship Sanjuro is on in the second level. It is possible that Monolith was thinking about having movies play between levels to move the story along instead of static pictures or static text.
The semi-obvious content is buried in the test resources. There are sound files and even fully animated characters that depict what would have happened during the levels. There were at least two levels that were taken out. The first one would have been after the level where Hank drives a truck into a garage and yells "Get your ass in the back." There was supposed to be a level where Hank drives the truck and tells you how he met Kura and why he is helping you. He would have given a speech about how he found Kura underground and why he wants to be a hero even though he never passed the physical tests to be in the UCA military. The level would have ended with enemy soldiers attacking and Sanjuro needing to clear them out.
The other level would have happened once Kura was rescued. This would have brought a flashback to Sanjuro's kindergarten days with Kura, Kathryn, Baku, and Toshiro at the UCA military academy. A glimpse of what part of the level would have looked like is in the intro movie where you can see kiddie Sanjuro walking towards a basketball goal. The game would have had Toshiro in danger of falling off a roof and Sanjuro finding a flower for Kura while also attempting to save his brother. What you did and how you did it would affect how characters dealt with you and also would have affected Kura as well as what she said when she found out that you and her sister were dating. Footage of this level can still be seen in the intro of the game. Also, Sanjuro's child model is still in the game's data files. Typing in the cheat code "mpmecha" (which changes your MCA into a different model during mecha missions) turns Sanjuro into the child model during infantry missions.
The game also has some trouble with some versions of ATI drivers, which cause the menus to be invisible (and consequently the game to be unstartable), or can cause textures to load improperly or not at all (resulting in a totally grey world). Updating the drivers generally cures the problem.
There was also a multiplayer bug. This allowed you to install the multiplayer-only part of the game, and then be able to access the single-player from the multiplayer menu.
During cutscenes hitting escape to access the main menu and then return to the game gives the player partial control of Sanjuro. This is most notable at the end of the game where you can actually kill Kathryn and Kura as they chase each other around the during the credits.