Resident Evil 5 is notorious for its stiff controls, frustrating partner-AI, obtuse interface, questionable quicktime events, and an incredibly silly storyline. As one would expect, these elements don't make for the most compelling single-player experience.
However, the game's co-op mode is incredibly fun and rewarding.
The Standard Co-op Setup
Most action games encourage players to work together by turning a Prisoner's Dilemma into a Trust Dilemma, i.e., making it so that helping each other out is always the most beneficial course of action for everyone involved. To achieve this, friendly-fire and other possible sources of griefing are diminished or removed, enemies are tweaked to take on the firepower of multiple players, and player-goals are designed around non-competitive challenges, e.g., everyone gets an achievement for defeating the boss instead of one person getting an achievement for the most kills.
Healing a defenseless comrade is another common mechanic that ensures players try to help each other out. Letting a partner die diminishes the chance of success -- or can even result in a game-over screen -- so all members of a team can usually depend on friendly aid. This in turn fosters a reciprocal relationship facilitated by special indicators that display the location and status of everyone else in the group.
Forcing gameplay-cooperation at specific script-points is common as well, e.g., having one player boost another to higher ground in order to proceed. While these sound good on paper, such statically-defined activities are rarely as satisfying as letting the players come up with their own strategy for traversing a level. With that said, scripted gateways serve to differentiate the gameplay and ensure that each player feels like part of the team.
All of these co-op elements are present in RE5, but there are many more as well.
All The Extras
A great example of something that's conducive to cooperative play is RE5's shared-healing mechanic. Whenever any healing item is used (except for the eggs), both characters get healed if they're standing close to each other. This encourages players to communicate and plan rendezvous points in order to get the most value out of their reserves.
Communication is also made easier by the fact that all firearms come equipped with laser sights. Laser sights allow players to point directly at areas of interest simply by aiming at them. The visible laser-pointers reduce the amount of explaining needed for proper communication, and they're cleverly implemented as they give a secondary function to an existing mechanic.
Another interesting element is that both players must activate the map-exit in order to transition to the next area. Some players complained about this being a bit inconvenient, but I personally thought it was a great decision. Having a loading screen suddenly pop into view while sniping an enemy can be quite jarring. The wait mechanic prevents this from happening, and it allows both players to fully explore each area without feeling rushed.
Whenever one player activates the exit, his point-of-view also swirls around to show his teammate. This is a neat little touch as it informs the player to the whereabouts of his partner, which in turn let's him quickly decide whether to stick around at the exit or go back into the field.
Money is another important asset in RE5, and here the game takes a cue from a various co-op RPGs. In order to prevent players from squabbling over treasure, both players simply receive the full monetary value of each collectible. While this is definitely not realistic, it prevents anyone from worrying about splitting the loot and keeps the focus on the action.
Finally, the level and enemy designs make it beneficial to communicate and devise on-the-spot tactics. Maps tend to be closed off arenas with multiple paths, and they allow players to split up and cover each other from different vantage points. This is especially important when fighting the more powerful enemies as attacking them from alternating directions helps expose their weak spots.
The above mechanics enhance the standard cooperative template, but there's one more element that makes RE5 special.
From Good To Great
Each player has a 9-slot inventory, and all items take up a single slot. Some items can stack within a slot as well, but only up to a point.
While this might seem like plenty of space, the real estate is at a constant premium.
The weapons in RE5 are differentiated by their damage output, area of effect, firing rate, range, penetration, clip size, and chance of scoring a critical hit. The enemies and environments are well tuned to these attributes, creating situations where one firearm is much more useful than the others. Since each weapon also requires a custom ammo-type, it's impossible for a single player to hoard all the goodies. Instead, each player must take on a specialized role.
For example, one player keeps a group of enemies at bay with a shotgun while the other snipes some archers in the background. Or one player pilots a vehicle while the other showers fast-moving opponents with a semi-automatic. Or one player leads a boss up a path with some explosive barrels, while the other uses his handgun to blow them up from above.
In addition to the standard firearms, though, the inventories must also accommodate healing items, armour jackets, and miscellaneous other collectibles such as proximity bombs and stun rods. It's very easy to fill up the available slots, but the ability to trade items alleviates the issue.
Trading also encourages additional cooperation, especially when one player's path leads him to stacks of ammo for the other player's weapons. Although enemies never drop ammunition for weapons neither of the players possess, forking paths often force players to collect items they don't really want. This in turn creates a unique flow to the game: an area is entered, its enemies are dispatched, the players scavenge for loot, and finally they regroup to heal up, trade, and get ready for the next challenge. The pattern doesn't keep the players tightly tethered together, but it always brings them back to help each other out.
Like most co-op games, RE5 ultimately needs players to cooperate with each other; progress can't be made if one person refuses to play along. If both people are on the same page, though, the game's rich tactics and inter-player interactions elevate it above the co-op modes of its contemporaries.