- You will now fly through a large space fortress. This fortress will contain many enemies along both the top and the bottom of the stage, often through narrow corridors. As you fly through the stage, it's a good idea to remove the prepositioned enemies as quickly as possible, even if that means flying closer to the right side of the screen. The threat that remains after that is the Duckers who walk on to the screen from the left and follow the terrain of the ship up and down.
- All of the four power meter arrangement but the second have the ability to shoot upward, whether it's the Double weapon of types 1 and 3, or the 2-Way Missiles of type 4. Making use of these weapons will improve your chances of survival. Only type 2 lacks an upward fire. While its incredible firepower may have enabled you to reach this stage, this one weakness will become evident here. However, the enemies don't exploit blind-spots or cluster up together nearly as intensely as they do in the racde version.
- Before entering a narrow tunnel, Zabus will begin to materialize. They appear as trios in a single columns throughout various locations on the screen. They tend to make appearances staring on the right side of the screen, and working their way back to the left. Be on guard when they appear, and move out of their way if you can't destroy them with your Options.
- The Zabus take a break when a set of three hatches appear, one on the bottom and two on top. The upper left hatch is a bit difficult to remove without some means of upward fire, but the other two should be take out as quickly as possible. Beyond this point, the Zabus will continue to appear until the speed of the scrolling suddenly increases as you enter the middle portion of the stage.
- This portion of the stage is a nod to the intense sixth stage of the arcade game which features high-speed scrolling through the maze like corridors of a space fortress. Though not as complicated or vast as the arcade game, the increased speed will still require you to rely more on reflexes and gut decisions. Although the tunnels and paths through the fortress are fixed, you must constantly evaluate the current situation and make split decisions about which way to move.
- There are three particular obstacles that you must be especially careful around. The first are giant stationary orbs which are found periodically throughout the fortress. They are exactly the height of the pathways they roll through, so they leave no room to squeak by without crashing in to them. Your only hope is to shoot at them until they are destroyed. While you are only forced to contend with orbs in the very beginning, there are times where choosing to destroy one can open up a path that is safer than the alternative.
- The second obstacle are large collection of particles that occupy certain patheways. Normally, it's not too difficult to blast a path through them. However, since you are likely to be encountering these at a very high rate of speed, your chances to punch through them are diminished. It is best to pick one particular height at which to shoot, and stay there the entire time. If you have Options, it's best to line them up on the same height with you to improve your chances.
- The third obstacles are gates. Gates open and close as you attempt to pass through them. When they appear on the screen, they are typically closing, and they will open back up before they leave the screen, making the far left side of the screen a fairly safe bet for passing through them at a good time. Keep yourself level with then center of the gate to maximize the time you will have to fly through the gates. A long collection of gates mark the end of the speed portion of the stage.
- Once high-speed scrolling ends, the next challenge will begin: the tiles along the floor and the ceiling will rip off from the surface and fly straight towards the Vic Viper as if drawn magnetically to it. While this occurs, tall columns of Zabus will appear on the left. The tunnel will narrow as the tiles break off and fly towards you, forcing you to shoot your way through them in order to survive.
- As you fly through the tunnels, it is possible to position yourself just right so that one set of tiles flies just above or below you. After you survive the flying tiles, the space will open back up and a few cannons will be waiting for you on the floor and ceiling. Then the scrolling will stop, and you will encounter the next challenge; the Intermediate Fortress. You will know you have arrive when a large orb crosses the screen from left to right, and the floor and ceiling disappear.
- Once the entire array is assembled, there will be a series of small guns surrounding an opening to the core, which is ultimately filled with barriers. Two domes along the top of the bottom open intermittently to release Duckers. Unlike the arcade version, you can actually destroy the domes to prevent any more Duckers from appearing. The guns fire small bullets that can fill the screen and make it particularly difficult to find safety. If you make it here with at least two Options, you can attempt to adopt a strategy to stay safe, remove the guns, and attack the core, but it truly takes all four Options to remain motionless throughout this fight. Fly from the top to the bottom, or the bottom to the top, and spread your Options out so that the second one is firing down into the barriers, and ultimately the core. The first and third options will end up destroying the gun array, while the Vic Viper destroy the Duckers and ultimately the dome. With some patience, you will wear down the barriers and destroy the core.
- After the battle with the Intermediate Fortress, you will begin another gauntlet to the next challenge. You will return to regular fortress combat conditions, except that now different parts of the floor and ceiling will rise or lower to particular heights, creating new channels for you to fly through. Once again, having the ability to fire upward is extremely helpful here, and Duckers approaching from the left are particularly dangerous.
- When narrow tunnels appear, try to remain inside them for as long as possible to use them for cover. A feature unique to this conversion of the game are the small guns which appear from the sides of the elevated or lowered walls. They aren't difficult to clear, but their presence may take you by surprise. Wait until the walls settle into position before attempt to fly beyond them.
Boss: Crab[edit]
In an amazing technical feat, the developers of this conversion were able to pull-off the inclusion of the full screen moving boss known as the Crab. Animating such a large on-screen character such as this is not trivial for the Famicom to accomplish. Once you reach an are where the floor and ceiling level out and the enemies stop appearing, fly over to the right. Duckers will begin to appear above and below, while the Crab approaches slowly from the left.
It has six legs, three on top and three on the bottom, and it makes its way from the left to the right. Unlike the arcade version, you can actually destroy the Crab by shooting it enough. In fact, if you have a long trail of Options, you can possibly clear it away before it even reaches the right side of the screen by flying straight to the right across the middle of the screen so that the center of the core is struck by the left-most Options.
Assuming that you don't have this much fire power, you must first dodge the Crab as it walks to the right so that you can fly back to the left and shoot it. This means committing the Vic Viper to the top or bottom half of the screen, and slipping beneath the legs as they lift up and advance to the right. Crab has no weapons of its own, but the Duckers which occasionally appear on the floor and ceiling will be shooting bullets at you, and these bullets can pass through Crab, so be careful.
Once Crab reaches the right side of the screen, it will hesitate, shake its torso, reverse course and return to the left. You only have two opportunities to fly through either of the two left most legs. If you miss it and are stuck on the left side, you will die when you collide with the legs. After it reaches the left side, it will decide to go back to the right for a while. It will continue to walk back and forth until you have shot at the central core sufficiently to destroy it. Then you can advance to the final stage.