The second-player Luma isn't essential to Mario's existence - the pudgy plumber has plenty of tricks of his own - but it does make his life a little easier. A power up that may have required Mario to launch himself perfectly onto a high altitude cloud can be plucked from the sky and gently handed over for the hero's consumption. A particularly fearsome patch of bad guys can be stymied when the second player shakes the Wii remote at an enemy and stops him in his tracks until Mario can muster up a series of spin attacks. Or, a few star bits that spill from a defeated baddie can be absorbed by Luma instead of falling out of Mario's grasp.
Amanda aids me not by simply using the gameplay mechanics available to Luma, but by giving me advice about what to do next with Mario. Because she doesn't have to worry about saving her own skin as Luma, Amanda's attention is freed up to look closely at what I'm doing and spot a tactic that I may have overlooked - a platform that might lead to a secret area or a better way to tackle an enemy that was giving me trouble.
In one of the early game worlds, I had initial difficulty with a two-legged robot boss that launched little drill-shaped robots directly at me. I could defeat the mini-drills, but Mario kept bouncing harmlessly off of the boss's legs. How was I supposed to take him down? It was Amanda who suggested waiting for the robot to show its glass-domed star between its legs and line up Mario. Then I'd use my handy drill-bit power up and dig through the small planet, pop through the ground on the other side and attack. I heard a satisfying cracking sound of the glass, and Amanda and I both cheered as I eventually destroyed the boss.
It was a moment of pure cooperation and teamwork between two players in the same room, a real rarity in games.
In contrast, most co-op videogames are better described as "self-interested team-ups" defined by players selfishly pursuing their own goals over helping each other. Co-op players often try to rack up more kills than the other players or grab the loot, power-ups or ammo first before any of their teammates. Call of Duty: World at War even features a "competitive co-op" mode, which is kind of an oxymoron if you think about it.
Because of the "me-first" nature of co-op, Valve intentionally crafted special zombies designed to pick off Rambo players in Left 4 Dead. In other words, teamwork was forced as a game mechanic. In Super Mario Galaxy 2, teamwork is more organic, due to one player acting as a passive helper-character. The idea makes sense to Amanda, even if it baffles lifelong hardcore gamers and many game journalists.
Several prominent game reviewers panned the co-op in SMG2 precisely because of the limited interaction that Amanda found so enjoyable. Co-Optimus, a website that specializes in covering cooperative games, gave SMG2 an overall score of 5 out of 5, but only 3 out of 5 for the co-op system because "it isn't the same as playing as Mario" and is "a far cry from real co-op." PopMatters critic Arun Subramanian, meanwhile, speculated that the SMG2 co-op was "clearly something of an afterthought." Similarly, IGN editor Colin Moriarty called the co-op system "half-assed" and lamented the lack of turn taking co-op from the original NES Super Mario Bros. games. It's not surprising that critics would assume that Nintendo's co-op system for SMG2 was designed as a half-hearted throw-in, because assigning the second player to a lesser role is a relatively new concept in games.