Metroid Fusion

Metroid Fusion, also known as Metroid 4 (メトロイドフュージョン, Metoroido Fyūjon) is the last Metroid game chronologically and first Metroid game released on the Game Boy Advance.

Metroid Fusion is different from other Metroid games as it is very linear compared to the other games and introduced a non-playable computer character to direct Samus where to go and what to do there, thus making sequence breaking harder and exploring the maps nearly impossible.

Story
The story starts out with Samus Aran helping Biologic Space Laboratories researchers on planet SR388. Eventually, a Hornoad confronts them, which Samus kills. However, a strange object comes out of the Hornoad and enters Samus's body.

Thinking nothing of it, she went on with the researchers and completed their assignment. Back on her gunship, Samus was returning to the Biological Space Laboratories station when disaster struck. The thing that entered her body on SR388 was later found out to be an X Parasite, or simply X. Once the X had infested Samus's central nervous system, she lost consciousness while she was in her gunship and drifted into an asteroid belt. Her ship's emergency systems automatically ejected the escape pod before impact, though the gunship itself was lost. Biologic's vessel recovered the escape pod and transported Samus to Galactic Federation HQ. However, as she was being transported, the X multiplied within her, corrupting large areas of her Power Suit.

Due to the X infesting her, the organic components of Samus's Power Suit had become so integrated with her system that it could not be removed while she was unconscious. Large portions of her suit had to be surgically removed, dramatically altering her suit's appearance. However, the X in Samus's central nervous system were too embedded to be removed safely, causing her to be given less than a 1% survival chance.

However, a cure was found. The X were the prey of Metroids. Unfortunately, due to Samus destroying all the Metroids on SR388 in a previous mission, the X were able to multiply without anything stopping them. Thus, to destroy the X in Samus, doctors proposed using a Metroid cell to make an anti-X vaccine. Apparently, the Federation had managed to preserve a cell culture from the same infant Metroid that saved Samus while she was on Zebes a second time. The serum was prepared and injected without delay, causing the X parasites to be completely eradicated - with two side effects. Due to the vaccine, Samus could no longer be hurt by normal X - in fact, she could absorb them. She also became vulnerable to cold, as most Metroids are.

Afterwards, Samus was given a mission. Samus was to travel to the Biologic Space Laboratories research station. During her surgery, the research team sent the last batch of creatures captured on SR388, as well as the infected pieces of her Power Suit. A large explosion rocked the station, which Samus was sent to investigate. Her mission on the BSL station would also be be overseen by her ship's computer.

Once she lands in the docking bay of the ship, Samus goes to the Quarantine Bay to investigate the explosion. At the Quarantine Bay, she finds a Hornoad and kills it. However, Samus finds that the Hornoad contained an X parasite. Samus speaks with her computer and learns that the specimens brought back by the field team were infected by X parasites. The X can mimic its prey, meaning anything organic could have hosted it.

During that time, Samus' computer analyzed the information about the X. The parasites invade and rapidly reproduce, killing the host creature. They also absorb DNA and use it to mimic the host. Samus was almost killed by the X, though thanks to the Metroid vaccine, she lived, due to the Metroids being the main predators of the X.

As she continues to explore the station, Samus finds a startling discovery. X have turned into an incomplete form of Samus, known as the SA-X. The SA-X came from the capsule containing her infected suit parts and used a Power Bomb to escape the Quarantine Bay. That explosion also opened the capsules containing all the X specimens, causing them all to be released.

As Samus progresses through the station, she finds another startling discovery. She finds a section of the station known as the Restricted Lab. Here, she finds dozens of infant Metroids behind glass, and most of the other natural forms of Metroids in stasis. The Federation never mentioned anything about cloning Metroids to Samus before. Suddenly, the Mertoids break free, apparently by the SA-X. In an attempt to destroy its predator, the SA-X decimates the Restricted Lab, releasing many infant Metroids as well as setting the area on fire. A fire alert then begins, causing the lab to be locked down. Samus barely escapes, and the lab falls off from the research station and explodes, killing all the Metroids (and the SA-X within).

Samus speaks with her computer, who is angry with Samus for discovering the Metroids. The computer explains that the Federation has been secretly working on a Metroid breeding program - for "peaceful application". The computer goes on to say that SRX, a replica of the SR388 ecosystem, was made ideal for for raising Alpha, Gamma, Zeta, and Omega Metroids. This research even uncovered techniques for rapid growth - allowing an infant to become a Gamma in mere days instead of months, years, or centuries. However, the X had found out about this research - apparently through a crew member infected by X - and was the one who destroyed it. The computer then indicates that because the X reproduce by asexual division, there are no fewer than 10 SA-X aboard the station.

Later, the computer tells Samus that they're done on the station and to leave the rest to the Federation and to evacuate the station. Apparently, the Federation has taken an interest in the X and SA-X and believe this life-form has endless potential applications. However, Samus is strongly against this as she knows how dangerous they are.

Samus knows that as soon as the Federation ships land, the X will overwhelm them and absorb the knowledge and power of their occupants. The X are just waiting, and then they'll spread across the universe. Galactic civilization will end.

Samus then proposes to activate the station's self-destruct mechanism to destroy the X on the station and on SR388, willing to risk her own life to get rid of the X.

However, Samus's computer has locked her in the Navigation Room. She demands to be released, though the computer says it has been ordered to confine her until the ships arrive. Samus then says, "Don't let them do this. Can't you see what will happen, Adam?" Adam Malkovich was Samus's previous commanding officer, who died saving her life. Samus tells the computer this, though mocks her. The computer goes on to say that detonating the station in high orbit would not guarantee the complete extinction of the X parasites, even though the station would be utterly destroyed. Samus would only succeed in removing the one obstacle to the galaxy's ruin: herself, stating, "When Adam decided who would live, he chose incorrectly."

However, a very strange thing suddenly happens. The computer suddenly changes to a different personality. The computer tells Samus that if Samus were to alter the station's orbit, then she might be able to include the planet in the vaporization field of the self-destruct detonation. It ends with a very familiar tone to Samus: "Any objections, Lady?"

Samus goes to the Operations Room, though is confronted by an SA-X. The SA-X is defeated, but manages to escape into a nearby ventilation shaft before Samus can absorb it. She starts the self-destruct sequence and returns to her ship. Hoever, she finds the docking bay in ruins with her ship gone. An Omega Metroid suddenly appears, immune to Samus's weaponry, even her Ice Missiles. The Metroid attacks Samus, leaving her incapacitated and badly wounded. As the Omega Metroid prepares to finish her off, the SA-X arrives and interferes, pushing the Metroid back with the Ice Beam. The Metroid counterattacks and defeats it, causing it to revert back to it's parasitic form. Samus absorbs the X and is able to regain her Ice Beam (going into the Omega Fusion Suit) and with it finally defeats the Metroid. Her ship reenters the bay, piloted by the computerized Adam and the same Etecoons and Dachoras she saved on Zebes (and earlier in the game in a habitation area).

As Samus leaves the station, it crashes into SR388, destroying both the station and the planet, ridding the universe of the X.

Samus then reflects on what she did. She doubts people will understand why she destroyed the X and the danger that was barely averted. Tribunals will be held and investigations. Samus believes she will be held responsible. Adam understood this, and told Samus, "Do not worry. One of them will understand. One of them must." Samus goes on to say that "we are all bound by our experiences. They are the limits of our consciousness. But in the end, the human soul will ever reach for the truth... This is what Adam taught me."

Gameplay
The gameplay is very linear. Samus's CO gives a series of objectives throughout the game, and is capable of locking and unlocking doors and hatches to ensure she achieves her objectives before she can progress. These include acquiring powerups, defeating enemies, and reaching certain areas. However, these objectives usually require a solution that is not immediately obvious, giving you some room to explore.

The environments in Fusion also change throughout the game in much more radical ways than in other games in the series. For example, some corridors become permanently blocked by explosions, parts of the research station being destroyed to prevent access ever again, and new creatures that appear in previously explored areas. Some gameplay elements differ significantly as well, including disabling single-wall jumps, mid-air bomb jumping and other methods commonly used to perform sequence breaking.

Samus spends most of the game being stalked by the SA-X, which appears unexpectedly in various locations. Due to Samus having the Metroid vaccine, she is susceptible to ice. Since the SA-X has the Ice Beam, Samus must hide from it whenever it appears.

Much of the gameplay also involves Samus downloading data to obtain power-ups. Since she is using the Fusion Suit, she doesn't have much equipment at her arsenal, requiring the Federation to create it and send it to her on the station.

Almost all of the creatures in the game are actually X parasites mimicking other lifeforms. Creatures are usually reduced to floating X cells when they are destroyed. Samus can absorb these to replenish her lost energy and missiles. However, if Samus does not absorb them, they can re-form into new enemies or disappear entirely. Some monsters can also absorb additional X parasites, evolving into newer, more powerful forms.

Graphics
The graphics are very similar to Super Metroid ' s and are rendered in 2D. The overall graphics and animations are also slightly more detailed. The game is a side-scroller, so like the rest of the 2D Metroid games, all of the action is displayed from a side-on angle. Metroid: Zero Mission uses a highly modified version of Metroid Fusion ' s game engine.

Equipment
Samus begins the game with little equipment. Since her Power Suit had to be removed and replaced with the Fusion Suit, almost all of her abilities were removed as well. She must retrieve them through either downloading the data from terminals scattered throughout the station, or through absorbing certain powerful X parasites..

The Jump Ball and High Jump abilities are also combined into one item. Her regular orange Power Suit is now the organic-looking yellow and blue Fusion Suit. Each type of missile will simply replace the last rather than being a separate kind of weapon, and regardless of what kind of missile is being fired — normal, super, ice, or diffusion — it will only ever use up 1 missile. Power Bombs also have a blast radius that takes up the whole screen, making up for the absence of the X-Ray Scope.

Adam Malkovich
Adam was Samus's commanding officer during one of her assignments with the Galactic Federation. Very little is known about this mission or about Adam himself, other than that Samus has great respect for him and that he gave up his life to save Samus. In the game, Samus stated that Adam called her "Lady" on her missions and if any one else had said it, it would have sounded sarcastic, whereas from him, it was respectful.

Special features
Owners of both Metroid Prime and Metroid Fusion can unlock new features in Metroid Prime using the Nintendo GameCube Game Boy Advance Cable. If you complete Metroid Prime, you can unlock Samus's Fusion Suit for use in Prime; if you complete Metroid Fusion, you can, depending on the game version, unlock an emulated version of either the original FDS version or the NES port of Metroid. There is also a bonus to be had by linking to Metroid: Zero Mission — the entire Fusion gallery of pictures is unlocked in Zero Mission, including the extra ending images from the Japanese version of Fusion which chronicle Samus's early years, and some additional concept art.

Reception
Metroid Fusion was very well received. The main criticism came from the game being so linear. According to Metacritic, the average rating for the game is 92.

Trivia
The Metroid Fusion instruction manual states that Metroids were actually created by the Chozo to prevent the spread of the X parasite. However, the word "Metroid" means "Ultimate Warrior" in the Chozo language, suggesting that there may have been other reasons for their creation as well.