Destroy all invading spacecraft.
Destroy all of the invading spacecraft and win.
Slay 100 alien rippers.
Kill 100 alien rippers to unlock this achievement.
Slay 100 alien shock troops.
Kill 100 alien shock troops to unlock this achievement.
Slay 100 arachnid crawlers.
Kill 100 arachnid crawlers to unlock this achievement.
Slay 100 worker aliens.
Kill 100 worker aliens to unlock this achievement.
Slay 20 alien rippers.
Kill 20 alien rippers to unlock this achievement.
Slay 20 alien shock troops.
Kill 20 alien shock troops to unlock this achievement.
Slay 20 arachnid crawlers.
Kill 20 arachnid crawlers to unlock this achievement.
Slay 20 worker aliens.
Kill 20 worker aliens to unlock this achievement.
Slay 5 alien rippers.
Kill 5 alien rippers to unlock this achievement.
Slay 5 alien shock troops.
Kill 5 alien shock troops to unlock this achievement.
Slay 5 arachnid crawlers.
Kill 5 arachnid crawlers to unlock this achievement.
Slay 5 worker aliens.
Kill five worker aliens to unlock this achievement.
Slay 50 alien rippers.
Kill 50 alien rippers to unlock this achievement.
Slay 50 alien shock troops.
Kill 50 alien shock troops to unlock this achievement.
Slay 50 arachnid crawlers.
Kill 50 arachnid crawlers to unlock this achievement.
Slay 50 worker aliens.
Kill 50 worker aliens to unlock this achievement.