Taken directly from the Kotaku article...In the Wii's Modern Warfare Squad Mate mode, a second player can use a second remote to fire off shots at enemies, but has no control of the movement and only their reticule will appear on the screen.
It's kind of like a shooter's version of Co-Star Mode, the cooperative two-player option in Super Mario Galaxy that had one gamer playing while the other fired off stars to help out the main gamer.
"It's like Super Mario Galaxy's support mode," said Daniel Suarez, executive producer for the game. "I can drop in and out at any time during the entire single-player campaign. I can pick up weapons, reload and support the main character."
While playing as a Squad Mate, the main player's gun remains jutting from the center of the screen. The secondary player has a different colored reticule that can be used for aiming and shoot. During scenes where the screen is zoomed in, such as for sniping or when using a mounted weapon, the secondary player can't shoot.
There are very few other differences between the Wii version of the title initially released for consoles two years ago.
"Everything that was in Modern Warfare is in here," he said. "We have not left anything out, it's undiluted. All of the single player maps down to the number of AI are there."
Online multiplayer includes all of the same maps and modes, the same experience system and ranking and the unlockables. The Wii version will have some changed in online play, including a decrease to a maximum of ten players online.
The online mode will also support host migration, which means that if the host of an online match disconnects the game won't end. Suarez said the they've also included the ability to import your list of friends from the Wii into the game so you can see if they are playing the game when you are and invite them into a match directly without having to reenter their friend codes.
"Our hope is that it will have the same addictive nature of playing online on the Wii as the original does," he said.
To bring the game over from the Playstation 3 and Xbox 360 to the Wii the team at Treyarch had to spend a significant amount of time optimizing and improving the engine last used to create Call of Duty: World at War.
"We did lots of optimization," Suarez said. "It improved the overall experience of the game. It has better texture optimization, optimized fire effects and explosions."
The Wii title also supports the same sort of fully customizable controls first seen in Wii shooter The Conduit.
"Since Conduit people want to be able to customize their controls," he said. "So we've given them the developer's tool box. You can change everything."
Watching Suarez and another developer play through the Sins of the Father level, the game certainly captured the feel of the original Modern Warfare and included all of the audio and cut scenes.
The colors seemed a bit washed out, but Suarez later told me that he though that was a product of the television not the game. I did notice that many of the straight lines in the game were jagged.
The game's explosions and weapons fire looked fantastic. Suarez says the game runs at a consistent 30 frames per a second.
"Our goal is for people who own a Wii and have never played this game on another console before to buy it," he said. "We think there is a large group of people who haven't played Modern Warfare."
