It's been said a lot, but this really must be one of the very best shooters ever made. It's just a shame that the single-player game is so short, with only ten levels. It's a lot of fun while it lasts, though, and the multiplayer mode is awesome.
I do have a couple gripes other than just the short single-player mode, though. For one thing, interior environments often appear pretty generic and repetative. There are rooms and halls that I swear I had walked through many, many times, but in completely different locations in the same level. For another thing, around the end of the very last stage, the game credited me for reaching a checkpoint while I was in a location that turned out to be deadly. Unfortunately, this means that I got stuck in a mortality loop whereby I die there, only to start over at the last checkpoint... which is right where I died. I just died over and over until I restarted the stage.
Those gripes aside, this game was wonderful, if a bit short.
graphics = 10
sound = 9
gameplay = 9
play control = 9
replay = 10
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overall = 9 (not an average)