After the introduction, you will appear underwater. Swim up immediately to avoid the tentacles. Once at the surface, go right. On the next two screens, you will see slugs dropping from the ceiling and crawling along the ground. Crouch down, and kick them as they get near. Make sure you kill all of them, because you will be coming back here later. Keep going to the right, and the beast from the background will appear in front of you. Run to the left and don't look back. After you pass the first screen with the water, get ready to jump on the next screen, and catch the vine. You will end up swinging around behind the beast. Run again, this time to the right. You will eventually be stopped by aliens, who will shoot the beast and then you Survivor.
You will wake up in a cage with another alien who becomes your friend. Start swinging from side to side and the cage will end up falling on the guard. Your friend will say something to you, and when he starts running away, grab the guard's gun (by crouching). Stay crouching here for another 30 seconds and a UFO will fly in from the top left of the screen Secret UFO.
Don't use the gun too much, or it will run out of power. Run to the right until your friend runs past you to the left. Start shooting now to take out the guard that was chasing him. Keep running to the right and your friend will start trying to open the doors. Create a shield on your left First shield and kill several more bad guys. As soon as the door is open, run through.
You will come to a lift - go up first and look through the window Explorer. Now go down twice (one floor below the one you started on). Go to the left and you will come to a door you cannot open. You should see a power line running beneath the guard's feet at the base of the screen. Go back to the lift and go down again. As you walk off-screen to the left, start shooting to kill the guard. Fire at the left wall to disable the power line leading upwards (towards that guard). Now go back to the door you couldn't open (and make sure your friend is following close behind). Blast it open using a "mega-blast" (hold the fire key down for a long time, then let go) Mega shoot. Quickly run to the left and go down using the teleporter. Run off the left of the screen and wait for your friend. Go up through the teleporter and your friend will open a floor panel for you to fall through. Roll to the left once you are in the pipes.
Roll slightly to the left until you are next to the first steam jet. Wait for a break in the steam and then roll past. Roll left and drop down, then roll right and do the same with the next jet. Keep going right and you will fall down between two jets. Roll to the right, drop down, then left and down and fall off the bottom of the screen to the right.
You will land in a large room with a strange chamber on the left. Go inside to recharge your gun Warrior. Mega-blast each of the three doors and continue to the right. Run through the tunnel to the right and kill the single guard. Keep running and you will come to a missing bridge. Take a running jump and you will land on a small ledge below. Blast a hole on your right and run through the hole.
You will now be in the caves below the next building. Go to the right and drop down the first hole, then drop down to the left - note the light colored piece of rock you land on, as you'll be using this later. Fall to the right again and you will land on a large, T-shaped rock formation. Drop to the right and jump off the ledge over the stalagmites. Keep going right for the next two rooms, dodging the rocks (they fall with a certain pattern on each screen). Run past the tentacles because they can't grab you if you keep moving. Also watch out for some jaws in the floor - you can jump over these with a standing jump. On the next screen, shoot the tentacles to make them retract, then run and jump over the jaws in the floor. You will eventually come to a wall that you should blast open. You will be swimming through this entrance later.
Go back past the jaws and tentacles until you reach the falling rocks area. You will take the path upwards and avoid the rocks this time. Shoot at the red bat hanging in the cave and follow it to the left - it will get eaten by the tentacles and you will now be safe. Leap onto the nearest stalactite, climb up slightly and keep leaping to the left. You will end up back on the T-shaped rock.
Fall off the left side and mega-blast the support. You can now run up the ramp to the right. Keep going right and jumping over the holes in the floor until you reach an expanse of water. From the left edge of the screen, use a mega-blast to free the water. Quickly run to the left and jump over the holes. As long as you don't stop or slow down, you'll make it to that light piece of rock and get blown upwards to safety Escape water. Head over to the right until you reach a wall. Mega-blast the wall and head right. Go upstairs and further right, past an algae covered area (that used to be a waterfall). Keep going right.
As you enter the building, you will see your friend crawling just beneath you, and getting blocked half way along the passage. Go left, back down the stairs and right again past the algae. You will arrive in a room with chandeliers hanging from the ceiling. Go down the stairs and get ready to shoot a guard. Head right again. Ignore the stairs on this screen and keep running right along the ground. A guard will punch you, then pick you up and shake you. When you come to, kick the guard (fire button) then run over and get your gun, spin around and shoot him Cowboy. Go right again and you'll enter a very difficult room.
Go almost half way to the second pillar and form shields on both sides of yourself. Move slightly more to the right to make guards appear from both sides. Keep up your shields, and mega-blast the shield of the guard on the left, then kill him. Replenish your right shield, and kill the other guard in the same way. Now go back to the chandelier room and shoot the middle chandelier (from the top of the stairs). This will free your companion. Head left past the waterfall, up the stairs and right again (to where your friend used to be trapped). Make a shield about two-thirds of the way towards the right of the screen and then go right. Your friend will slide past in the lower left corner of the screen and a guard will appear on the right. Quickly run left and hide behind your shield on the previous screen. Kill the guard when he appears. Continue to the right and shoot at the fleeing guard in the next room. Follow him to the right and you will find him behind three doors. If you open the doors he will shoot you; if you have a shield prepared he will roll bombs that can get through your shield. The trick is to form a shield, open the doors and close them so that the bomb rebounds and kills the guard. After this, go through and mega-blast the wall behind the guard, and continue to the right.
Above you is a recharger - you can use it if you want to, but your gun should never run out again anyway. Go further right and you will see a domed area with three green spheres. You can see a reflection of a guard in the spheres. Crouch and wait until he stops moving and then shoot - he should get squashed. Go left to the staircase and go down. Use the teleporter to get to ground level and head right until you reach some water. Jump in and start swimming.
While you are swimming, don't pause anywhere or you will end up drowning. Head straight down and to the left (through the wall you blasted earlier). Keep going left until you are in a room with two passageways up and one down. Swim up the left the passageway and keep going up to use the air-space. Now swim down through the shaft leading downwards and over to the ledge. Do a standing jump to the right then continue right and shoot the power line in the wall. Go back to the left and use a running leap to get back into the water. Head back up to the air pocket, and then out the way you came in. At the surface, exit the water to the right. Keep walking right past the guard you squashed into a room with a shaft in the floor.
Drop through the hole and use a mega-blast to remove the door on the right. Start running! When you reach the right end of the tunnel, turn around and make heaps of shields. Your friend will eventually thrust his arm through the grate above you and pull you to safety.
Outside, you are set down on the ground and your friend runs into the building. Don't follow, or you'll get shot. Instead, run to the left and then to the right, so you end up going behind the building. Keep running to the right until you are on the other side of the building, and then run inside. Make a shield and kill the first guard, and your friend will take care of the other guy. Run to the right until you reach the ledge. If you fall off the edge here you will die Free fall. Wait until your friend beckons you to approach and do so, to be thrown across. Wait for him to jump, and then take a standing jump to the left. You will end up on the ledge below. Quickly run slightly to the right then turn around and form a shield. Take care of the two guards (if you don't go to the right first, you won't be able to kill the second guard). Run to the left and into the next room.
Keep running to the left past the staircase. Three unarmed guards will run away, but one won't quite make it. Approach him slowly and point your gun at him. He will close all the doors in the complex. Mega-blast the door and kill him. Now go back to the right, and go up the stairs. At the top, jump to the right and form several shields. Mega-blast the guard's door and he will begin rolling bombs at you, but they will fall down the stairs. After he has thrown at least 4 bombs, kill him. Run over to the teleporter, turn to the right, and go down. Quickly make two shields to your right, mega-blast the guy's shield and kill him. Run over and teleport down again. Shoot the powerline and then use the teleporters to get back to the stairs. Go down and fall through the hole in the floor made by the bombs.
Run to the right. The next room will be dark because you shot that powerline (if it wasn't, the guards below would shoot you). Stop immediately when you enter the next room and jump over the grate. Pull the lever on the wall to release a whole heap of beasts from their cages below. Now drop through the hole in the floor and start running to the right. Keep running until you reach a teleporter, and go up. Head to the left and you will find your friend, still hanging helplessly. Step onto the edge and you will release a bridge to save him. Head to the right and up another teleporter. Follow your friend down the ramp to the right, and into the juggernaut.
In the cutaway view in the arena scene, you have to press different buttons on the console to activate the escape pods. The aim is to turn two buttons green and two buttons red, and then finally press the white button that appears. Just pressing randomly should get you there Gladiator.
Run out of the baths to the right. As you reach the bridge, be prepared to fight off four guards Last battle. After that, keep running to the right and your friend will break through a stained glass window. Keep running, and you will be unable to avoid falling through a broken platform. You will be caught and beaten up a bit. When your friend joins the fight, start crawling over to the right. Wait until your friend gets knocked off the ledge before pulling two levers in quick succession. The first will kill the guard, and the second will activate a teleporter in the roof. Crawl back to the left until you are teleported up to safety, and the end of the game The End.
The final achievement is earned simply by dying a total of 50 times Determination.