The seventh stage is another stage that requires patience to clear safely. You begin just outside of a huge complex. Head inside and jump to the upper ledge. In general, it's almost never a good idea to follow the lower route through this stage. It's usually tougher and riddled with soldiers who will appear on both sides of the screen. Stop at the four mechanical arms ahead and study their pattern for a moment. When you have the timing down, make your way through them one at a time. These arms form the basis for the challenge that you will encounter throughout the stage.
Once you make it to the edge of the upper ledge an item capsule will fly by that contains a Fireball gun. If you still have the Spread gun, hold on to it. At the next ledge, there are more mechanical arms. Study the pattern and make your way past them. Pause for a moment at the edge of the ledge. If you have the Spread gun, shoot the Gunner on the higher ledge before continuing on. If you don't, just fall to the bottom and move past the mechanical arms there. It's very difficult to destroy the Gunner from the lower ledge, and if you try to climb back up, the Gunner will easily attack you, so don't try. When you get through the mechanical arms, make a short hop to the edge of the next, raised ledge. Destroy the spike wall that pops up from the ground, and each subsequent wall that appears.
Once you've done that, jump to the edge of the upper ledge and destroy the spike wall there. Soldiers will begin pouring in from the left and some of them will try to jump to the ledge that you occupy. If they succeed, turn around, crouch and fire at them. You should kill them before they're able to reach the ledge. Continue to the right and move past the mechanical arms ahead. Then destroy the spike wall at the other end. Fall off the ledge and use the mine cart to get onto the ledge above you. The nearby weapon sensor contains a Barrier. Collect it, and run right through the mechanical arms ahead. Jump onto the mine cart heading to the right. If you can't collect the Barrier, don't run past the mine cart, or it will run you over and cost you a life. Once you pass two of the walls, jump onto the ledge above you and kill the sniper. Then jump across the large gap to the ledge of the right.
Jump at the edge of the left ledge to clear the gap. If you miss the other side, fall to the lower right edge of the screen, onto the mine cart below. Then hop off of the cart and continue to the right past the mechanical arms. If you made to the top right ledge, destroy the series of spike walls ahead. Then fall off the ledge and destroy the set of spike walls in front of you. Fall down to the lower ledge and continue to the right. There are more mechanical arms ahead to get through. A spike wall will pop up just beyond the arms. You'll have to move left and right as the mechanical arms go up and down in order to stay alive, while you fire at the wall. When you pass this obstacle, you’ll be back on the outside. You'll encounter two Gunners and more soldiers that arrive from the left. Once you reach the slightly higher platform, another Gunner and more soldiers will appear. Defeat them to reach the boss.
Boss: Alien lair defense
This battle is similar to end of the first stage, but considerably tougher. There are only two enemies here; soldiers which will either appear from the door or from the far left, and a modified variety of Turrets which fire bullets into the air that split into three before they hit the ground. There are locations where you’ll be safe from the blasts. However, the turrets alternate, so you have to pay attention to where the blasts are going to land. If you find them too difficult to avoid, you can attempt to destroy them. If you only wish to destroy one, attack the one on the right. When the siren goes off, head to the far right and fire at the flashing panel above the door while avoiding the turrets. With the Spread or Laser gun, you can destroy this boss in very little time. It will take a bit longer with other weapons.