Map 20: Gotcha!

Complete Doom II Map 20: Gotcha! walkthrough, including secret locations, Supercharge pickups, and strategies for defeating tough enemies.

Walkthrough:

1. Shoot the Shotgun Guy in front of you, then turn around and use your Chaingun to snipe a Shotgun Guy and an Imp through the narrow window behind your start.
2. Turn back, open the door in front of the first Shotgunner, and be ready to fight a Chaingunner, two Imps, and two more Shotgunners.
3. After clearing the enemies, grab any dropped weapons and walk forward in the passage until you reach the two torches. Wait for Imps to appear from either side and shoot them.
4. Walk forward a few more steps; the two steel columns in the center of the large room will lower. The left column has a Spider Mastermind, and the right has a Cyberdemon.
5. Go to the east side of the room on the perimeter ledge. Let the Spider Mastermind's chaingun shots hit the Cyberdemon, causing them to fight each other. Pick off the survivor.
6. Drop into the low area. On the north side, facing the bridge between the platforms where the bosses stood, find a Supercharge.
7. Go to the south side of the room and use the elevator to return to the perimeter ledge.
8. Backtrack out the door to the starting area. Facing the narrow window, walk forward very slowly until you reach the ledge's edge. A green circular platform will rise from the blood below. Wait for it to finish rising, then walk around it and through the door in the back of the small building.
9. Inside, quickly shoot the Chaingunner on the high platform to the left before entering the building to claim the Super Shotgun and Shells.
10. The door acts as an elevator; lower it, stand on top, and when it rises, run to leap onto the platform where the Chaingunner was to get a Medikit, Armor, Health Bonuses, and the Chaingun (or ammo).
11. Exit the building and walk to the back of the circular platform, turning to face the door. Drop into the pit to the left of this door to find a Large Cell Ammo pack and a Radiation Suit in a cubbyhole (SECRET 1/7).
12. With the Radiation Suit, go around the building to find a cubbyhole on the opposite side housing a teleporter back to the level's start.
13. Turn back to face the door in front of your starting position. Strafe right and drop into the blood (ideally with the Rad-Suit). Find a small opening in the wall in front of you. Head through it and up the staircase into a dark room.
14. Prepare your Super Shotgun or Plasma Gun for a Shotgunner, a Chaingunner, and a Hell Knight in the confined space.
15. Shoot the east wall with a bullet or shell-operated weapon to make it rise. Head through the passage leading north.
16. At the window, use your Chaingun to pick off a Chaingunner and an Imp behind the large window opposite.
17. Run forward and drop into the lava pit surrounding the building. Go around the right side of the building to the back, near the east wall, to find another Supercharge.
18. Quickly run back to where you dropped into the lava and get onto the safe white-pebble ground. Find a skull switch on the wall.
19. Flip the switch to lower the nearby platform, ride it up, and shoot down the Imps in the narrow corridor.
20. Head through the corridor. Another platform will automatically drop down; get on it and ride it up. Claim Health Bonuses.
21. In the next corridor, shoot down a Chaingunner and an Imp. Collect the items and ride another automatically-descending platform up. Repeat this process, collecting items and defeating enemies like Chaingunners and Lost Souls, until the last part of the building.
22. At the end of the last building section, grab the Berserk pack just before a teleporter back to the start. Before taking the teleporter, examine the wall in front and to the left to find a hidden doorway (SECRET 2/7).
23. Take the white teleporter in the secret passage to warp to the top of a tall column, telefragging a Pain Elemental. Quickly shoot down any spawned Lost Souls and the two Cacodemons attacking from the sides.
24. Drop into the blood below and enter the small alcove to the south to find another Radiation Shielding Suit. Peek out to shoot any remaining Lost Souls or Cacodemons. The skull switch here lowers the column you warped onto, in case you need the Medikit on it.
25. Grab the Rad-Suit, hit the skull switch to lower the column, and get onto it. When it raises, run to land on the semi-circular ledge just right of the