Air Fortress/Stage 6

Entrance approach

 * 1) Three sets of wave motion enemies will greet you in this stage, followed immediately by the fast retreating round ships.
 * 2) As soon as you see energy items between two platforms, rush in and collecting, then collect the bomb item underneath as you fly back under the lower platform.  Then you can make your way to the top of the screen, and collect the next energy items above the barriers.
 * 3) You must then navigate through a set of passages between large columns.  Energy items can be found at the top and bottom of the screen between each pillar.  Be selective about which ones you go after, don't risk your life to collect every one.
 * 4) Slow retreating enemies will immediately precede a large twin beam ship.  After you destroy it, you'll see a bomb item on the ground.  As you approach it to collect it, rotating cubes will fly onto the screen.
 * 5) An energy item will be between two platforms.  On the other side, hatch enemies will fly out.  Then wave enemies will fly over the top, while you can drop down and collect a hard-to-see bomb item near the floor.
 * 6) Drifting triangular ships appear, followed quickly by Enterprise-shaped enemies.  Before you fly between the platforms to collect the energy item, destroy the barrier above it so that you can fly up to the next platforms and collect a second energy item.
 * 7) The last enemies you encounter before you reach the entrance are two sets of lug-wrench enemies, one barrier, and one set of slowly retreating ships.

Fortress interior
Things are going to get a lot more complicated from here on. Hopefully you've amassed a large amount of energy and bombs before you entered. You're going to want to be very thorough about clearing out enemies on your way to the core as you will have to retrace your steps in order to reach the Lightspeeder. The more enemies you eliminate, the easier it will be for you to make it out before the fortress explodes.
 * 1) From the entrance, head to the left and drop down to the floor.  Continue left, and you will encounter a clone.  Destroy it quickly with bombs, and continue left.  Destroy the robots before the elevator and hop in.
 * 2) Take the elevator down.  You will have a tough time getting out of the elevator with so many bullets flying towards you.  Do your best and destroy the two hopping sentries as quickly as possible before ducking into the elevator in the lower right corner.  You will probably take a bit of damage doing so, but it's best to remove them now.
 * 3) Take the elevator down, head to the left, and destroy the clone and hopping sentry that greet you.  Instead of destroying the mini-core to the left, head to the right, below the elevator.  Destroy the robot and the energy-wave shooter before the square cannons.  After you pass the cannons, another clone will attack you.  Remove it and fly to the right and get in the elevator.
 * 4) Ride the elevator down, and exit to the left.  Shoot the hopping sentry and continue left.  Destroy the two blue robots as you drop to the floor, then proceed right.  You must decide to deal with the energy-wave shooters and wall cannons, or try to ignore them and slip past them.  Another robot and energy-wave shooter await you before a mini-core.  Destroy the core, and the next one beyond it, watching out for the flame orb between them.  Continue past them and proceed to the elevator in the lower right corner.
 * 5) Take the elevator down and begin dropping.  It's possible to ignore the clone that falls with you, and all of the other enemies in this room, immediately duck into the elevator at the bottom.
 * 6) Go down to the room below.  Out of all the enemies that you face here, the biggest threat is the flame orb.  Destroy it as quickly as possible, then you can choose to destroy or ignore the remaining enemies as you float to the elevator on the left side of the room.
 * 7) Ride the elevator up to the next room, and stick to the left side as you float up.  Once again, the biggest threat is a flame orb that tends to occupy the space right beneath chute C, which is your destination.  It's hard to lure it out of the way, but do your best to avoid it as much as possible as you try to access the chute above.
 * 8)  When you arrive, destroy everything in sight before you maneuver down the cylinder channels.  When you drop down, a cylinder will be on it's way up, so you'll have to head back up, let it pass, and then drop back down below.  Pass the next cylinder to access the core.  Before you shoot the core, take out the two blue robots behind the core.
 * 9) You must be careful as you shoot the core, and watch out for the floor magnets.  When you destroy the core, you have an even bigger challenge; flying back over the magnets to get back to the cylinder channels.  You must touch the ceiling just as the first magnet begins to operate.  If you don't do this right, the magnets will pull you down before you can reach the cylinder, and you'll wast precious escape time repeating the process.
 * 10) Return through the chute you arrived at.  As soon as you exit from the next chute, immediately return through the same chute, and you will actually end up back at the starting point.  From here, repeat steps 1 through 4, except do not take the elevator that leads to step 5.  Instead, fly up through chute B.  You must make it through these steps as quickly and efficiently as possible as you will not have a lot of time to succeed.
 * 11) Once you pass through chute B, start falling down.  As you do, you will be barraged by a bunch of rotating cubes that fly up from the floor.  They will be very difficult to dodge, but do your best to reach the bottom.  Two energy-wave enemies will be waiting for you.  Stick to the center to avoid them, and shoot out the walls that block your access to the escape Lightspeeder.