Achievements:
     Complete   the   following   achievements  to  unlock  Xbox  Live
Gamerscore points.

Alien in Training (5 points) Complete level 1-1.
Hungry Yeti (10 points)      Eat 50 KGB Agents with the Yeti.
City Destroyer (10 points)   Destroy 25 buildings during one game.
Juvenile Alien (10 points)   Complete the game on the Easy difficulty.
Adult Alien (15 points)      Complete the game on the Medium difficulty.
Expert Alien (20 points)     Complete the game on the Hard difficulty.
Head Chomper (20 points)     Head bite 50 enemies without 
                             touching the ground or firing.
Killing Spree (15 points)    Kill 1,000 enemies during one game.
Mad Hatter (20 points)       Unlock all 31 hats.
Perfect Flight (30 points)   Defeat the final Boss without 
                             using a continue.
Survivalist (25 points)      Survive any challenge mode for 20 minutes.
WMD (20 points)              Reach 5000 km in Super Soviet Missile Master.

Easy Survivalist and Killing Spree achievements:
     Select  the  Area  51  Challenge.  Start by killing everything in
sight.  Wait  for the big metal robot to appear from the right. Do not
destroy  it.  It  does  not kill you. As soon as it enters the screen,
stand  directly under it and start shooting in the opposite direction.
You  will  kill  everything  that  appears  from the left side and the
enemies  jumping  over  the  robot  with  ease. Keep this up for about
twenty minutes to unlock both achievements at the same time.