K9

K9 is a single-level PWAD for Doom that was released in 1994. It was designed by Keith Sheehan and Dave Murray.

Secrets

 * 1) From the switch that lowers the yellow key, head east then north. Ahead is a secret door leading to a box of shotgun shells and a lift that leads to an invulnerability on hard skill. This secret sector is too small to receive credit for. (sector 72)
 * 2) After pressing the switch which opens up the yellow door to the east, head back down the stairs - as they curve there is a secret door to the south leading to a room with a medikit, a backpack, and 2-6 imps. (sector 200)
 * 3) The south-east corner of the room accessed by #2 has a niche to the south which lowers on entering - there is another lift opposite, which leads to a medikit and (on multiplayer) a chaingun. Between the two lifts is a secret door to the west, leading to four medikits, three boxes of shotgun shells, an armor, and a door to the main outside area. (sector 254)
 * 4) The room after the chainsaw corridor has windows to the west and east. Both of these lower on pressing - the western one allows access to the main outdoor area. (sector 126)
 * 5) The eastern window (see #4) allows access to another outdoor area. (sector 108)
 * 6) The main outdoor area has a building with a switch in the north-east. This switch reveals a switch en route to the switch which opens up the exit building, which lowers the window just to the east, allowing access back to the area with the yellow doors. (sector 123)
 * 7) After going through #5, head towards the barrel in the north-west. There is a secret door leading to the area east of #3. (sector 33)
 * 8) The room with the switch which opens up the yellow door to the east has a secret door to the north (next to the window) leading to a room with a chaingun on a pillar. (sector 177)
 * 9) After going through the blue door leading to the red key, there is a secret door to the east (opposite the window to the chaingun room) leading to a switch. This secret is too small to receive credit for. (sector 6)
 * 10) Press the switch behind #9, then head west, jumping over the gap and through a fake wall. Head south and jump over the nukage - a lift will lower, allowing access to three cacodemons, a soul sphere, and a megaarmor. The west wall of this lift is a secret door, allowing access to a ledge. This secret is too small to receive credit for. (sector 40)

Bugs
Due to secrets #1, #9 and #10 (above) being too small, the maximum achievable secret percentage is 70%.

Current records
The records for the map at the Doomed Speed Demos Archive are:

Player spawns
This level contains six spawn points:
 * 1) facing north-west. (thing 314)
 * 2) facing north. (thing 315)
 * 3) facing south. (thing 316)
 * 4) facing south. (thing 317)
 * 5) facing north-west. (thing 318)
 * 6) facing north-west. (thing 319)

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