• For this achievement, simply set game difficulty to hard and start Level 12. (hard difficulty because we want to spend as little time in the level as possible).
  
  
• Upon starting the level, simply run into all 5 humans and try not to die before collecting them all. Use Smartbombs to stay alive for this period of the level.
  
  
• Once you collected all 5 (or died before collecting all 5) just let the drones kill you. That way you can quick restart the level 5 times (using the 5 provided credits)

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If you are successful, you will get this achievement after about 15 - 20 Minutes, each round taking up about a minute. (you probably saved some humans in the normal playthorugh as well.)

• For this achievement, you should probably change the difficulty back to easy, or normal. Then start Level 6 (the sheep level)
  
  
• Just complete the level as usual (I personally think using the plus laser, which shoots in 4 directions, is a very easy weapon for this level)
  
  
• Once you can read Wave: final on the right side of the screen (after Wave: 7) you can kill all but one sheep (there will be 12 sheep, 3 in every corner) and let the last sheep kill you for a quick restart.

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you will get this achievement after about 20 - 30 Minutes, each round taking up about 2 - 3 minutes.