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The game starts you out as a Mechwarrior that has escaped the crash of the Icarus, your dropship. The first 'Mech you pilot is one called the Cougar scout 'Mech, a fast, agile 'Mech with the ability to use jumpjets. The first mission involves learning the basic controls of the game, destroying tanks, blowing up Hybrid Power Armor, and stepping on infantry.
XBOX LIVE! is where the game kicks it into high gear. Whenever you get a kill, run away from the mech you just blew up! The thermonuclear explosion will kill you, no matter what your armor level is at. The reccomended tactic is to use the Puma, or any other small, fast 'Mech with the PPC and/or jumpjets. Then be an ankle-biter. Most online players use the giant Atlas, Summoner, or Thor. Stay close to them so they cant hit you (Big mechs cant aim as low as their ankles), and pummel them with charged PPC blasts, then run when they blow up. If you have a fast 'Mech, you will get the salvage from the enemy well before the other people have a chance to get it.
Overall, Mechassault should be your first choice if you are looking for great online capabilities, an excellent action title, or you just want the