You must beat the level set called Base. It consists of 3 levels, in which you'll go back to Base 2, twice. (In order: Base 1, Base 2a, Base 3, Base 2b.) These levels are quick and easy. So it's best to look around for power ups and weapons to get a good start in the game. Try to save you're power ups.
level set: Base
Base 1
Base 2a
Base 3
Base 2b

Same story as the level set Base, but shorter. Look around for weapons and power ups, and try to save them. Just watch the first video, or the beginning of Re-cam (a minute or two in), if you get lost.
Level set: Warehouse
Bunk 1
Warehouse 1

A long, long set of levels. The game does start to get harder from here on out. There is tons of health on jail 2 if you need it. These levels aren't as straight forward as they were before. You will have to start looking for keys and CDs. As well as buttons and other methods to complete the sets from here on out.  Check out video 1 at 4:10 to end then video 2 from start to 1:11. On Re-cam it's 4:53-9:15

The first boss is on the last level of the set (security), he's not to bad. A chain gun brings him down quickly in medium or easy, but you can skip him all together.  Watch the beginning of the second you tube video. What you do is rush around him and when the tank turns the gate brakes, it's a trigger mishap. The gate is supposed to brake once the tank leaves the grate (as in died), but since it leaves it when it has to turn, it breaks. Then just rush down it. The time it starts in video 2 is 0:50-0:58 Re-cap video is 8:55 and stops at 9:03

Level set: Jail
Jail 1
Jail 2
Jail 3a
Jail 5
Jail 3b
Jail 4
Jail 3c
Security

A long, long set of levels. The game does start to get harder from here on out. There is tons of health on jail 2 if you need it. These levels aren't as straight forward as they were before. You will have to start looking for keys and CDs. As well as buttons and other methods to complete the sets from here on out.  Check out video 1 at 4:10 to end then video 2 from start to 1:11. On Re-cam it's 4:53-9:15

The first boss is on the last level of the set (security), he's not to bad. A chain gun brings him down quickly in medium or easy, but you can skip him all together.  Watch the beginning of the second you tube video. What you do is rush around him and when the tank turns the gate brakes, it's a trigger mishap. The gate is supposed to brake once the tank leaves the grate (as in died), but since it leaves it when it has to turn, it breaks. Then just rush down it. The time it starts in video 2 is 0:50-0:58 Re-cap video is 8:55 and stops at 9:03

Level set: Jail
Jail 1
Jail 2
Jail 3a
Jail 5
Jail 3b
Jail 4
Jail 3c
Security

You can skip the first level if you just jump over the bridge that gets exploded. For a fast way, watch from 3:55 to 4:03 in video 2, and in the re-cam video watch it from 12:22 to 12:34. They just rush across the bridge before it explodes [img]http://www.xbox360achievements.org/images/misc/a.png[/img] (bunny hop), then rocket jump (fire a rocket down at the ground while jumping) [img]http://www.xbox360achievements.org/images/misc/a.png[/img] away from the blast. The second way is to use a invulnerability power up so you can just cross the lava. You can also rocket jump, grenade jump,or barrel jump across, I recommend the first two, but the second one more as it's easier to do.

When you go complete fact2 and go back to fact1, look right, theres moving pillars with lazer, go across this area. (see 5:07-5:15 on second you tube video) (13:41-13:44 on re-cam) then you're done with this level set.

Levelset: Factory
Factory 1a
Factory 2
Factory 1b

This level set is a little annoying, but there is a trick so you only really have to do 1 level. The first level can be done in 12 seconds watch from 5:20 in video 2 to see what you have to do. Or from 14:00 in re-cam. Before you jump out the side of the window, keep on going into the room, you'll see a BFG!!!!!! (Once you get the BFG start saving Cell ammo, you can kill the last boss in 3-7 hits with it as long as you have quad damage)

For the next level watch from 5:40 on video 2, and 14:19 on re-cam. when video 2 is at 6:10 and 14:55 at re-cam you will see they will rocket jump into the air, and hit a trigger that will blow up the door, making you skip the rest of the levels. What happens is there was a lost switch that was never taken out of the game, and they hit it! I suggest you watch it from both first person and re-cam.

Level Set: Power Station
power Station 1
Power Station 2
(There are more levels but a trick to open the door elimanates the need to go to the other areas. Just read above!)

You can skip the first level if you just jump over the bridge that gets exploded. For a fast way, watch from 3:55 to 4:03 in video 2, and in the re-cam video watch it from 12:22 to 12:34. They just rush across the bridge before it explodes [img]http://www.xbox360achievements.org/images/misc/a.png[/img] (bunny hop), then rocket jump (fire a rocket down at the ground while jumping) [img]http://www.xbox360achievements.org/images/misc/a.png[/img] away from the blast. The second way is to use a invulnerability power up so you can just cross the lava. You can also rocket jump, grenade jump,or barrel jump across, I recommend the first two, but the second one more as it's easier to do.

When you go complete fact2 and go back to fact1, look right, theres moving pillars with lazer, go across this area. (see 5:07-5:15 on second you tube video) (13:41-13:44 on re-cam) then you're done with this level set.

Levelset: Factory
Factory 1a
Factory 2
Factory 1b

Most of the levels here are straight forward. With no real short cuts but one; I'll get to that. The first level you can just rush into the door you need to go into (see video 2 at 6:56-7:08 Re-cam 16:00-16:13), it's done in 8 seconds.

The second level has no shortcuts and you have to do things in order. There is one thing that is easily missed; taking the commanders head. After you go down into the lower floors, after you lower the bridge and walk across it, there are 2 buttons on the side of it. Jump across from the bridge and push them, then go back from where you came in untill there's a doorway on the left. Go in it and go on the elevator, grab it and proceed down it. Then return to the first level. Once it loads, walk into the door straight ahead on to the third level. (If you still can't find it, look at video 3 at 00:12-00:40 and on re-cam it's 17:05-17:35)

The third level is quite easy. You can skip the whole platforming puzzle by rocket jumping onto the platform. See it on video 3 at 1:46-1:46 and in re-cam at 18:50-19:00. It's quite easy to do the jump puzzle regularly, but it's just annoying as hell.
Then go through the pipe, keep on going in until you see a big opening on the left of this room. There should be some creates, some med-kit's and a door on the other side of the room. Go into the opening on the left then turn around and look up. Once you see a window and a switch, quad jump into the window. Once you hit the switch go to the right (looking away from the window) and exit the level. See it in video 3 at 2:02-2:18 and in re-cam at 19:05-19:22) If you can't quad jump, just continue thru the rest of the level normal. It's not to hard. (see FAQ at the bottom to learn how to quad jump)

Now the second to last level of the set; You can skip 4/6 objects here if you rocket jump into the window at the start of the level before you enter the building (the windows above the door). Shoot the computers on each side of the walls through the bars (I suggest using the grenade launcher to shoot through the bars and saving before you rocket jump and before you shoot the computers). Then go down enter the door and take a left into the door, then a right, you'll see a rocket tank. If he didn't see you, rush into him, duck, and walk past him, then run to the elevator (or rocket jump up if you want to). If that's not working before you rush into him, rocket him so he steps back and then rush past him. Once up, go around the cat-walk into a door. Once past that take a right, you'll see another tank. You can again rush then duck, or rocket and rush past. Then go through that door then go to either side, as the exit is in the wall behind it.
See how he beat this level check out video 3 at 2:23-2:49 and on re-cam at 19:28-19:55.

The last level of the set is quite straight froward. Just keep on taking rights, soon you see that there's an opening on the left; it is the only option. So go left and you will see a big pipe laying on the ground, after you go through the cave. Once you do, save, jump behind it and take a left, walk into the end section. An air strike will be called in after you put the air strike beacon on the side of the pipe. A door will open on the right side with 2 baddies coming out. You'll be safe inside that bunker if you're low on health. Come out after the air strike and you'll see the door that was locked by the beacon now is blasted open, go into it and you will be at the exit soon. See this level on video 3 at 2:49-3:50 and in re-cam at 19:55-20:54

Level set: Hangar
Hangar1
Lab
Hangar1ii
Hangar2
Command
Strike

You have to do 2 sets for this one, and the beginning level set is a Bitc.... I mean really annoying. It's easy to get lost. So if you do, the first level set starts in video 3 at 3:50-7:23 Start watching in re-cam from 21:00-24:55. As long as you follow the guide, you can skip a few levels.

It's important that you have at least 1 invulnerability, and 1 quad damage for an easy last boss (as well as an easier time in the first level set), but luckily 1 of each can be found in the first level set. (if you followed the guide you should have both at 2, or at least both at 1. As I said, save those power-ups.)

When you start If you bunny hop fast, you can jump into the gate before it closes. (watch at the time for both videos above in the beginning. You'll see what I'm talking about) If you jump on the flying strogg, the gate won't start closing untill you hit the floor, making it easier. If you can't make it just take a left once you go out of the door. then climb the rock stairs. Then step on the button across the balcony. It will open the gate, then just walk on the sides of the wall at the trap floor. When the floor opens up and tries to drop you in the lava, you'll be on the side of the trap door instead of falling.

After the trap thur the gate, keep on taking lefts in-till you fall into a giant hole filled with water. Once there take a right, you'll see a grate around the corner. Shoot at it with any weapon, (use the blaster, it has unlimited ammo) Make you're way up the stairs, up the ramp in-till you can walk straight into a room. You'll see a CD behind glass, shoot the glass, grab the cd, and run out of the room. Take a right and jump across into the door way, and again drop into the water. This happens at 4:08-4:35 in video 3, and in Re-cam at 21:17-21-27

Once in the water, go the other way this time, and take the elevator on
the left. Once there you'll enter the next level. There is A invulnerability power up in the level that is not show in the video. In video 1 at 4:53, instead of rushing in, go up the ramp in front of you and turn around. Kill the 2 baddies behind a railing and then head up the stairs on the right. If you shot the barrel behind them you will notice an opening, if not you will see a gate, Shot the gate if it's there and crawl under it. Keep on climbing the ladders in-tll you reach the very top, you will see an invulnerability power up on the left in front of some bars. Then go back down from were you came , crawl back under the vent and follow the video.

Ok back from were you came. Save, then with you're back to the door, take a right. If you're decent you can easily rush like he did (if you're rushing set quad damage on quick select, and have you're chain gun or supper shotgun out), if not take you're time. and head all the way to the other side of the level.
Once you're at 5:17 in video 3 (Re-cam at 22:26) get ready for a fight. Once passed the door use a quad damage if you have it (anothers coming up soon so it doesn't matter), then use the supper shotgun, or the chaingun to slice thur the baddies like warm butter, without quad damage, it's a lot harder. You can also use invulnerability instead (or use both if you want, recommend that you do) if you have 2, as it's best to save one for the final boss. If you don't have 2 invulnerability or 1 quad damage. You will have to take you're time on both sections, (or use the invulnerability away, this part is way harder then the last boss) as you need as much health as you can get once you go up the elevator.
Once there all dead, or the elevator comes down, grab all the health and armor if you're hurt. Theres a few packs up the elevator as well. If you don't have around 50-60 health by the time you have the med packs before going up the elevator, theres one on the right, you'll see a door, enter it. theres a med pack right in front of it, just don't jump down. To see all this watch it from video 3 at 5:17-5:37 and in re-cam at 22:26-22:48)

Ok time for lots of loading screens but, you're around the end of this level set. Once up take out everyone in the front, and use the door on the right. It's important that you do not get damaged much here. As you need to rocket jump soon. Head down and you'll come across a corner that leads up a ramp Save before you go around it. Just pop in and out around it using the grenade launcher or you're favorite weapon and kill. Once most of the baddies are down save, then rush in using an supper shotgun. If you rush around the right.You can avoid the sentry gun from spotting you early, avoiding it. (the baddies blocking the hallway at 5:47 in video 3 won't be there (Re-cam 22:58), as they will rush out when you're killing the others in the room.

Once up the stairs and past the door, theres med kits and ammo for bullets type weapons in some of the cells. If it's clear, save. After that use the supper shotgun, go into one of the cells, stay there, turn around, and look up.There are two stroggs on the catwalk that will come to you, you can kill them without them being able to really hit you. Once dead. Rocket jump onto the platform take the CD then go back down to the elevator. You can see him rush this section (not recommended) in video 3 at 5:35-6:05 and in Re-cam at 22:51-23:20

Once down the elevator head left. Enter the door and jump down into the pit. Kill the two baddies and push all 3 keypads/buttons on the computer. A cd will pop up in front of it. take it. head left (facing the super computer) grab some med kits and climb up the stairs, and rush back to the elevator. (you can rocket jump up to the cat walk like in the video, but it's far from needed.) See it happen in video 3 at 6:07-6:47 and in Re-cam at 23:25-24:20.

Ok time for the quad damage power up pick up. Head back to the end of the level were you picked up the CD on the catwalk, but stop before the sentry gun. Face the sentry gun but backpetal into the lava then rush out of it, there will be a quad damage pick up and some health packs in front of you. See it at 6:55 in video 3, and 24:29 in Re-cam.
After you go up the elevator, go up and thru the door to under the catwalks. Rocket jump back up on the cat walk and a wall should open up. (see video 3 at 7:01-7:06 and from the Re-cam at 24:23-24:40) then go thur the door on the right coming out of the keyboard room. once past the door take another right, then go straight. Then keep on going to the Keypad on the wall. Hit it and a bridge right next to it will fall down in a few seconds. Be sure to grab the med packs next to the keypad and rush to the exit switch. See it happin from Video 3 at 6:50-end of video, and in Re-cam at 24:24-24:55

Level set: Palace
Outer courts
Lower Palace a Invulnerability power up
Upper Palace a
Lower Palace b
Upper Palace b Quad Damage power up

Again there this amount of levels if you follow the guide and skip the levels.

After that last level set, you would think the last boss would be hard, but nope. His level set consist of 2 levels. 1 being 40 seconds long. with no short cuts. The other just being the boss fight. Remember when I said to save those power ups and the BFG? Well get ready to use them. To watch both levels in about a minute check out video 4, or 25:02-end video

The first level is just getting some ammo and health, nothing hard. Just some easy switch puzzles. this level is about 40 seconds long so just get any extra ammo you need and/or heath packs.

Now time for the final boss. Again the begging is just getting extra ammo and heath. once you make it to the boss turn on quad damage and invulnerability. Then take out you're BFG, and kill both his forms (you can kill him before you're power up even go away!).
If you don't have to BFG, the chain gun works well also. If you don't have the power ups, use the BFG and run around like mad. If you only got the chain gun/other weapons it will be a harder fight, so run around, and shoot with all you got.

After he's dead walk on one of the switch on the sides and go down the elevator on the same side as the switch you hit. Then enter the escape pod thats open. Push the button in the pod and beat the game. Watch you're ending scene and obtain you're last achievement. I think I just achieved carpel tunnel syndrome.

level set: Makron
Pre-boss
Boss