The fourth stage is a more difficult version of Stage 2. There are more rooms, and the enemies are more aggressive. The power core seals also have shields on them. To destroy the cores, you must blast the shields until they crumble and reveal the seal. You'll have to be much more vigilant and avoid the increase in enemy fire in order to stay alive. Remain crouching until it's safe to stand up and continue your assault. Naturally, the Spread gun makes survival in this stage easier, but it's quite possible to complete the stage without it.
- Room 1
- Destroy both turrets to the left and right of the lock, then concentrate on the seal to move onto the next room.
- Room 2
- This room contains four seals, but none of them are shielded, and they are all on the bottom. Crouch down and fire at each seal while avoiding the gunfire overhead.
- Room 3
- A turret is mounted on the wall above two seals. It isn't necessary to destroy the turret, but doing so can make removing the shields and destroying the seals much easier to accomplish.
- Room 4
- The configuration of this room may resemble the previous room, except that the turret and seals have been moved down. The turret is not easily destroyed, but you can crouch to attack the seals and remain safe. A red soldier will provide you with a Barrier.
- Room 5
- Focus on the single turret in the center before you work on the seals on either side. A red soldier will provide you with a Rapid fire upgrade.
- Room 6
- This simple room contains a single seal, and slots for rolling mines to appear. Line yourself up with the seal and the rolling mines should miss you. Crouch when necessary, but concentrate on the seal to advance quickly.
- Room 7
- Destroy the turret, then jump up to shoot the seal above the turret.
- Room 8
- Destroy the turrets to the left and right of the lock quickly, then fire at the seal to destroy it. Ignore the turret above the seal.
Boss: Terminal 2
This battle will be similar to the previous base's final battle. Begin by destroying the power core in the way of the turret, and destroy the turret as quickly as possible. When you begin shooting the turret, two types of robotic defenders will appear from the sides; the red shooting robots and the white gliding robots. A group of these robots will appear roughly every ten seconds in alternating waves. The shooting robots appear, stop above you, and fire three bullets at you. Theses red robots have decent aim. Shoot them while they’re still moving around if possible. The white gliding robots will move to your general area and try to jump on you. They are much easier to kill. These two groups of enemies will appear endlessly until you destroy the turret and the power cores.
Note that you should destroy the turret first before the rest of the power cores or the waves will continue when the boss appears. This boss is composed of four phantom images that move along the black section at the top of the screen. You can only damage the boss when two of the phantoms intersect with one other. When they do, they’ll stop for a moment before separating again. They each shoot out small bombs that travel slowly while trying to home in on your location, before speeding up in your direction. If you have a Spread gun, simply stand in the middle and fire upward. You may have to occasionally jump over the orbs if they get too close. If you don’t have a Spread gun, concentrate on one side first and then move on to the other side. Try to shoot down the bombs so you don’t have to move around too much to defeat this boss.