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- This is the final push against the invading Bacterion army. You will be taking the fight directly to their headquarters from where their leader has staged the invasion. You will be flying through an open alleyway through their large technological fortress. You can guarantee that the defenses will be tight. Be prepared with as much fire power as you can muster. Have plenty of speed too, but not so much speed that you can't navigate through small passageways without colliding.
- It is arguable whether have double-shots is more valuable than having lasers in this stage. There are a number of enemies attached to the upper layer of the fortress, and double-shot does allow you to pinpoint them in a direct attack. But sticking with lasers allows you to blast through numerous enemies at one time, provided you find a chance to climb up to the portions of the screen that are occupied by high enemies. If you are loaded with Options, then you can arrange the Options in such a way as to always be near the top so that they can destroy high enemies for you.
- The final stage is characterized by the tight spaces created between the upper and lower layers of the fortress. At times, they can come together to form very narrow passageways that you must safely navigate through. Don't take too many Speed-Ups or you may find it difficult to situate yourself exactly where you want to be in order to be both safe, and do maximum damage to the enemy.
- One enemy that is even more of a threat than usual are the Duckers. Duckers always appear from the left side of the screen. While you think you might always be aware of their presence, they can appear when you least expect them to, like when you're aiming at the terrain enemies attached to the top layer of the fortress from a "safe" spot on the left side of the screen. Before you know it, a Ducker may appear without warning and destroy you. Use your Options to destroy the higher enemies and stay safely in the middle of the stage.
- Flying enemies provide a nominal threat to your flight through the fortress, but the biggest threat to your survival are the showers of bullets that you'll have to squeeze through in order to stay alive. The more firepower you possess, and the longer you allow certain enemies to remain on the screen, the more flooded the screen will become with bullets. At that time, you may need to rely on your Shields to take on a number of the bullets in order to clear out a safe path.
- Throughout the stage, the will witness the reappearance of Zabus. Zabus were last seen in Stage 2 as the sub-boss before your fight with the Big Core. They appear in groups of columns as you fly through the fortress. They will only appear once you arrive close enough to their spawning point. You can trigger them to appear by rushing forward, and then retreat while you concentrate your fire ahead of you. Most of the Zabus will simply float into your line of fire and be destroyed.
- For the few enemies that do sneak by you, and fly off to your left, be especially careful of bullets that are fired at you from behind. Whether you have Shields or not, nothing can defend you against an attack from behind except your own survival skills. The bullets tend to blend in better against the lighter background of the fortress than they do against the blackness of space. Try not to fly backwards unless it's absolutely safe behind you.
- Towards the very end of the stage, you will be faced with a set of four hatches. Two are positioned above, and two are positioned below. The ones below are fairly easy to knock out with missiles, but the ones above are incredibly hard to hit, even hit double-shots. As a result, you are forced to deal with the swarm of enemies that pour out of the hatches until they are finished. If you dart forward to the opposite side, you may find yourself in an impossible situation, with a shower of bullets coming toward you. Try to position yourself to take out the top row of Rushes as they come pouring out, allowing your missiles to deal with the bottom hatches. You should be able to outlast the squads.
- You have a few more tests ahead of you before you can eliminate the leader of the aliens and destroy the fortress. The first comes in the form of this electronic cage that surrounds you. You can actually opt to avoid it entirely, but only if you have a good number of options, and only if you arrange them so that they remain to the left of you to destroy any enemy that sneaks up from behind. If you're daring, you can fly behind the cage, but you'll have to stay out of it's way once it's ready to leave the screen. It's actually not difficult to survive the inside of the electronic cage, since the "bars" come down in fixed positions, and the cage stops moving left or right. All you need to do is move up or down in accordance with the bullets that are fired at you from above and below.
- Once the cage is gone, there is another test. You will come to a wall, and the screen will stop scrolling forward. There are two arms that look reminiscent of the arms of a Tentacle, complete with the mid-arm weak point, extending from the wall. There is a gap between them, and some space to the right. As you stay there, the gap begins to close. The game is relying on you to realize that you must dash forward through the gap before it closes completely, or you will be killed by the impending collision with the wall. If you survive this trap, you will reach the ultimate leader of the Bacterion army: one giant brain. The brain is connected to the fortress' control system through six inputs, three above and three below. If you destroy those plugs, the fortress will initiate a self destruct sequence, you will be victorious in your mission. Congratulations! The game will start over from Stage 1 again at a higher degree of difficulty.