MAP15: The Theory of Broken Circles (BTSX-E2)


Back to Saturn X E2 maps 12-16

01 02 03 04 05
06 07 08 09 10 11
(12 - 16)
17 18 19 20 21 22 23
24 25 26 27
Secret map: 31

This level occupies the map slot MAP15. For other maps which occupy this slot, see Category:MAP15.

MAP15: The Theory of Broken Circles is the fifteenth map of the second episode of Back to Saturn X. It was designed by Björn Ostmann (Vader) and uses the music track "Geometry," composed by James Paddock (Jimmy). In the official add-on version, this level's name is Birdwatching in the Forbidden Realm.

The secret level, MAP31: Fireking Says No Cheating, is accessible from this level.

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Map of The Theory of Broken Circles
Letters in italics refer to marked spots on the map. Sector, thing, and linedef numbers in boldface are secrets which count toward the end-of-level tally.


Other points of interest[edit]


  1. From the map start, take the lift to the right. The wall to the left has a lighter patch in the middle. Press on it to lower it, revealing a passage (sector 140) where you can drop down on a soulsphere.
  2. In the green stone hall by the red key, the southern alcove with a green torch behind an inverted cross window hides a cross switch on the rock wall. Shoot it to open a wall north of the entrance leading to a platform (sector 490) with ten health bonuses and a computer area map.
  3. On the south-southwest edge of the map, there is a narrow cliff with a bloodfall on the south side. Go through this bloodfall (sector 500) to find two boxes of rockets, a blur artifact, and a floorplate.
  4. On the very west end of the map, in the C-shaped stone hall, a wall at the bottom end of the C is lighter than the rest. Open it to access ten armor bonuses, a bulk cell and a box of rockets. (sector 552)
  5. On the blood basin west of the C-shaped hall, run up the rock pillars to the north to reach the plasma gun on the island (the beige pillar lowers permanently; should you fail to make the crossing or fall off the island, a teleporter in the hallway to the north that takes you back to it). When you jump to it, an alcove with revenants will open. Inside this alcove is a cross switch behind the green torch; shoot it and take the teleporter nearby. Lower the wall with the lift-like texture to reveal a small closet with a tiny passage to a teleporter that takes you to a high ledge (sector 700) with a soulsphere.
  6. Near the northwest part of the map, on the ledge with the shotgun, hop to the black stone pillar to the south and then to the wall directly west of it. You'll land on a narrow, almost imperceptible staircase that runs along the wall. Climb to the top of it and a pillar will rise out of the blood. Hop on it as it rises (it can be lowered like a lift if you fail the jump) and when it reaches the top, hop off it and onto a ledge (sector 842) with nine health bonuses. From here, you can reach the opposite cliff to collect a megaarmor and energy cells.
  7. On the arena with the resurrecting revenants at the south end of the map, drop down to the blood below and up the stairs to the east. As soon as you climb the first step, you'll hear something open. Sprint up the stairs, onto the blood canal and through the bloodfall beside the hole in the wall to reach a hidden area (sector 1022) with two rockets and a megasphere.
  8. From secret #7, press on the grey wall with the face to lower it, revealing a circular room (sector 1382) with two rockets, a backpack and a floorplate.
  9. Stand in front of the blue key bars and turn right. Follow the hallway to a lift, and when it rises, stand on the west half of it. Once it reaches the top, run out of it; as it lowers, another smaller lift to the left will also lower. Ride it down to a small circular room (sector 1423) with two revenants, two stimpacks, three shotgun shells, and a floorplate.
  10. There are three teleporters in the map that cycle among themselves: one on the southwest near secret #3, one to the northwest by secret #5, and one to the southeast. From the southeast teleport, turn right and enter the dark staircase. At the top, go through the bloodfall, then turn around and head through the other bloodfall (sector 1395). This leads to a cavern with a stone mural depicting the map, with three cutouts indicating where the floorplates in secrets #3, #8 and #9 are (activated ones are dark, untouched ones pulsate green). After all the three floorplates are activated, the two pillars in the blood pit will be tall enough for you to cross over to the lift opposite the mural to the secret exit.
  11. From the lift mentioned in secret #10, cross the stone walkway and drop down to the blood when you can. Head northwest and through a short opening to find a pillar (sector 1253) with an energy cell, a bulk cell and a BFG 9000.


Demo files[edit]

Areas / screenshots[edit]


Routes and tricks[edit]

Current records[edit]

The records for the map at the Doom Speed Demo Archive are:

Run Time Player Date File Notes
UV speed (normal exit)
UV speed (secret exit)
NM speed (normal exit)
NM speed (secret exit)
UV max
NM 100S
UV -fast
UV -respawn
UV Tyson
UV pacifist (normal exit)
UV pacifist (secret exit)

The (absence of) data was last verified in its entirety on February 21, 2022.


Player spawns[edit]

This level contains thirteen spawn points:

  1. facing north. (thing 5)
  2. facing south. (thing 1293)
  3. facing south. (thing 1294)
  4. facing east. (thing 1295)
  5. facing east. (thing 1296)
  6. facing north-west. (thing 1297)
  7. facing north. (thing 1298)
  8. facing west. (thing 1299)
  9. facing east. (thing 1300)
  10. facing south. (thing 1301)
  11. facing south. (thing 1302)
  12. facing south. (thing 1303)
  13. facing north. (thing 1304)


Map data[edit]

Things 1614
Vertices 6896*
Linedefs 7059
Sidedefs 11096
Sectors 1493
* The vertex count without the effect of node building is 5470.


This level contains the following numbers of things per skill level:

Technical information[edit]

Inspiration and development[edit]


See also[edit]


External links[edit]