Level 22: Neptune Storage Depot
Enemies: Class 1 Drone, Class 2 Drone, Small Hulk, Super Hulk, Driller, Cloaked Driller, Heavy Driller, PTMC Defense Prototype, Platform (Missile), Spider Processing Robot, Baby Spider
If you’ve made it this far this level isn’t too complex. There are Drillers and Super Hulks but they’re in fairly easy positions to destroy without taking damage. The room ahead has 3 Super Hulks guarding the doors. Take them out from a distance or around corners to avoid the homing missiles.
When you are ready shoot a couple of Smart Missiles down the tunnel in the center to kill the Drillers. More will spawn as you enter the room below so back up to grab the Invulnerability and then fly down to take out the Drillers. Some of them will be cloaked. One of the side passages leads to the Red Door and is also protected by 2 Cloaked Drillers.
When you open one of the upper side doors you’ll see the Blue Access Key behind a grate. The Blue Door is in the floor and the Yellow Door to the right. Fly around to the left, past the Energy Center and take out the Super Hulks before picking up the Blue Access Key.
The Blue Door leads down to a lava level. There’s a few underground rooms here and the Yellow Access Key isn’t hard to spot.
Make your way through the Yellow Door which leads to a tower. Each window has a Driller behind it so take it out with lasers from an angle. Hopefully they won’t get any shots off on you. When you approach the top get ready for 2 Super Hulks. Use a Mega Missile to take out the first and damage the second. A few Homing Missiles should finish off the second Hulk. Fly down the center of the tower to find the Red Access key. Head back to the dark room with the Cloaked Drillers and go through the Red Door.
Reactor: The reactor is housed in a square structure in the center of the room. Pick up a Cloaking Device before heading in so you can take out the robots before focusing on the reactor.
Exit: Out through the Red Door and up through the passage in the roof to the exit.