- Easy Survivalist and Killing Spree achievements
Select the Area 51 Challenge. Begin 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 begin shooting in the opposite direction. You will easily kill everything that appears from the left side and the enemies jumping over the robot. Keep doing this for about twenty minutes to unlock both achievements at the same time.

- Hats
Successfully complete the indicated task to unlock the corresponding hat:


- Achievements
Do the following things to obtain the corresponding Gamerscore points:

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

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