You can't always judge a book by its cover, but Fuse's box art is fairly damning: four faceless characters, identified only by their glowing weapons. Throughout the six campaign missions, each broken up into three sections, you'll learn very little about these special operatives, beyond the fact that Izzy wields a Shattergun that can crystalize groups of enemies (for crowd control), that Dalton has a Magshield that can be used to cover your party, that Jacob has an Arcshot that fires charged, incendiary bolts into foes, and that Naya carries a Warp Rifle that can cause multiple targets to spontaneously implode. The most specific thing you learn is that Dalton's apparently afraid of cats, or so you're told in one of the many unskippable dialogue sequences that come as you shimmy up a wall or sneak through duct between gunfights.
Story isn't Fuse's strong point (did you expect more from generic baddies like the insane Russian Ivan Sovlenko or the sadistic Chinese Mao Meilin?), and as the title implies, it's all about your xenotech, Fuse-powered weapons. Everything else, like the fact that the Fuse energy might be sentient, is a throwaway moment, pacing to help better distinguish the sequences in which you duck behind cover and shoot everything that moves, attempting to combine abilities for extra experience points, such as shooting Izzy's crystals through Dalton's shield. Sadly, the AI also appears to be an afterthought, which renders the game largely unplayable at higher difficulties without human partners, especially since a Game Over is triggered whenever anybody on your team dies.
Sticking with the generic theme, Fuse also allows you to leap between these characters, so long as they're not bleeding out, and save for their weapons, they're all pretty interchangeable. Secondary abilities acquired later in the game make them slightly more unique (Izzy can heal the party with a ranged medical beacon and Naya can cloak for some of the stealthier sections), but this only really comes into play when dealing with heavier enemies, like the machine gun-, rocket-, or flamethrower-wielding Leadfoots, or during the lengthy and repetitive boss fights against flying robot Whistlers or leaping robot Enforcers.
Throw in the cloaking melee enemies and shielded elite agents, and the game feels like one long riff on Mass Effect 3, which isn't terrible if you loved grinding through that game's co-op multiplayer. (Yes, your characters earn money and experience, which are used to level up fairly identical skill trees and buy perks shared by the entire team, such as overpriced and bland new skins.) Echelon mode, where you'll be farming funds, is literally the same thing you've seen in dozens of other games: a series of waves (12) punctuated by slight variations on theme (kill everything, kill a specific heavy, defend a point, breach a point). These six maps are ripped directly from the campaign, too, so there isn't even anything new to do or see, and because Echelon has only one difficulty mode, the final few waves simply stack the odds ridiculously in the enemy's favor, especially if you aren't at the level cap (35) or playing with skilled humans who understand how to spam their weapon-overcharging Fusion ability.
To the credit of Insomniac Games, movement is as smooth as in their Ratchet & Clank games, and the shooting mechanics seem refined from their work on the Resistance trilogy. The hacky story is at least accompanied by a few good quips and the missions have a few neat diversions in which the party splits into smaller groups or gets timed. But none of this really excuses the banality of Fuse itself, which is missing the larger-than-life set pieces that might make the campaign pop, nor the redundancy of the gameplay, which gives you all these cool weapons only to have you do the same thing with them over and over again, regardless of whether you're on a space station or an underwater research facility. Like the Die Hard franchise, then, each new level plays to diminishing returns, a mindless exercise in action over substance.