Defeat the Alien Queen and complete level 1
Defeat the Alien Queen and complete level 2
Defeat the Alien Queen and complete level 3
Defeat the Alien Queen and complete level 4
Find the secret door, defeat the Alien Queen for the last time and rescue Newt
Defeat the Alien Queen equipped with the ShotGun
Defeat the Alien Queen equipped with the TwinPulse
Defeat the Alien Queen equipped with the SmartGun
Defeat the Alien Queen equipped with the SerboGun
Defeat the Alien Queen equipped with the FireGun
Defeat the Alien Queen equipped with the WaveLaser
Finish the game without dying once
In level 3, avoid the Alien Queen and go to level 4 using the underwater exit
Boost your jump to level 3, you're going to need it !