This is actually one of the only Acclaim games worth the lagg while playing. A small gem in the genre of free MMO's.
You begin the game by choosing one of three starting bots and then as you progress add parts and upgrades to improve you stats (Basic). The combat is also fairly basic, you join in of three different match types; Sector Battle, where you or a group of other players take on hordes of NPC bots while progressing towards a boss fight. Player vs. Player, in which 2-8 players form two teams or fight free for all until all of the opposing players are defeated. And finally Base Battles, in which two teams are formed and defend a base.
Once a match is completed EXP and Gigas (in game currency) are given to players according to there efforts in the match. If in some match types a player plays extremely well other forms of rewards are given which determine your stats.
The upgrading in the game is fairly simple and not to expansive but still satisfying and updates on the gear are fairly regular although it seems not much is done for the free users and to experience a decent updating service you need to pay real money to purchase the good items. That said every major event that is celebrated around the world is given an event item or something in the game. Everything from Christmas tree helmet's to national hug day body armor suit's are available for a certain amount of time.
But considering this game is completely free it's worth a look and has a fair amount of hours of gameplay if you persist at leveling up your Bot. I recommend the free online download and not going out and paying $5 us for the disk.