Green car in the parking lot emits music.

There's a texture of a man with a grill in the skybox near the nearby neighborhood.

In the skybox behind some trees there is a picture of a cat.

Behind the rightmost TV in the fitness center, there is a series of numbers and letters that leads to this video: https://m.youtube.com/watch?v=nJqq_XUkHPo
What's interesting is that the person who made this video has the same profile picture as the creator of this map. Possibly the same person? Another thing I noticed about this video is that the music in the video is the exact length of the video.

When using stormfox 2, the flag outside will change the speed of the animation accordingly to the wind strength (inconsistent, only happened once before in my experience.) In addition to this. The flag also makes noise.

Touching the electric box thingy connected to the utility pole out back of the building will hurt you.
Edit: proper term is "transformer"

Your Geiger counter goes off near random places outside, (water tower, abandoned shed, etc) and near the sludge pool.

After opening and closing the door to the dark room fully, it will lock for a while. (Probably to try to scare you if you were just exploring)

In the canals (or whatever you call it) near the back of the building, there is a pipe that hurts you if you touch it. Because it triggers the Geiger counter, it is presumed there was radioactive material going through the pipes. Other pipes in the canal do not hurt you in this way.

The Peace Garden stops ambient noise from playing, but does not stop ambient noise that was playing before entering the garden.

The singular stop sign in the map can be broken by running into it.

Spawning entities inside of the basketball court causes them to spawn inside of the floor.

Technically not a secret, but there is a divider in the party room that I did not notice before. You can press e on the handle to open it or close it.

In the pipe room, there is a puddle which can only be seen from an angle.

The cones near the sludge pool don't have collisions with the player. They can be re-enabled by disabling and enabling their collision through the c menu.

The fences near the playground are normal fences partially inside of the ground.

Inside of the melon/flesh head room, there is a series of numbers and letters above the cabinets which leads to this video. https://m.youtube.com/watch?v=1kpCoAbuqCQ

When knocking over the running kleiner in the fitness center, the water shelves behind him still get knocked over even when you prevent him from crashing into it.

If you enable the setting "Limit the Physics Gun" you will not be able to move the shelves in the fitness center.

When loading a save, many effects occur.
-turrets in food shop permanently turned on
-boxing bags in fitness center fall down
-two kleiners in treadmill (behind the scenes. When interacting with the running kleiner, he disappears and ragdoll kleiner is revealed. When loading the save, it breaks the whole thing and both kleiners are visible at the same time.)
-lifesavers on walls fall down.

Wall art near the lobby show barns with power plants and radioactive water. This may support the theory that the community center was previously a nuclear plant dealing with radioactivity, due to the large amount of areas where your Geiger counter goes off. The radioactive pipe in the canals strongly supports this as well. Either this, or the wall art is supposed to be about the two nuclear power plants seen in the skybox.

In the canals, near the van, there is a fish in the water.

The hoops in the gymnasium can be retracted when you press a button on the wall (hl2 elevator button)

Near the playground, there is a can in a bush. (Near where the kleiner spawns when pressing the admin "Clean Up Everything")

Kleiner inside of the women's restroom.
Surprisingly detailed.
Lines:
"I'm encountering unexpected interference!"
"My goodness."
"Fascinating."
"Dear me."
"This suggests an entirely new line of investigation."
"You must get out of here!"
"Thank goodness. my relief is almost palpable."

Actions:
-Sometimes flushes the toilet and then says a random line.
-Sometimes farts and then says a random line.
-Sometimes a small splash sound plays and then says a random line.
-When unlocking and opening the door to his stall through outside means, he says "You must get out of here!" (Info from glad0sb0y1)

According to another user (named Kleiner at time of writing), when you bring the radio near the van outside into the dark room, it makes SSTV sounds, which can be made into an image. This is the image extracted by the same user.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3292141483

dog barking ambient from the neighborhood i think, i couldnt really pin point where the sound was

a trigger that goes from the water tower to the open space near the center (showtriggers_toggle) and sets off your geiger counter, i think its supposed to be a pipe underground.

Thats my image!! :D
I guess it may be confusing how my username is "Kleiner" and Everything about this map is about Kleiner.
Edit: "The Electric Box thing" is called a transformer.

Originally posted by Kleiner:

Thats my image!! :D
I guess it may be confusing how my username is "Kleiner" and Everything about this map is about Kleiner.
Edit: "The Electric Box thing" is called a transformer.

Thanks, didn't know the proper term

Idk if anyone pointed this out, but if you hit the punching bags with a crowbar or gun, blood will come out. https://steamhost.cn/steamcommunity_com/profiles/76561198196031459/screenshot/2515906945695853993/

I think powerplant on the maps background might be a reference to CS De_Nuke

When you open the women's bathroom where Kleiner is sitting at, using Extended Propeties, he will say "You must get out of here!"

Interacting with outlet at the computer lab will insta-kill you

Almost everything!

there are dollar bill all over the map,one is at the cafeteria [the one that activates the turrets] and another at the vending machine where one of the kleiners spawn if you know what you do with these bill please enlighten me

If you break every window in the map kliener calls from the phone in the cafe and says that you ♥♥♥♥♥♥ up the entire project

Originally posted by dingledoof:

If you break every window in the map kliener calls from the phone in the cafe and says that you ♥♥♥♥♥♥ up the entire project

An easier way to hear the voiceline is by putting bombs in the computer lab. Strangely this doesn't break all the windows, but works anyway for some reason.

Edit: setting off a nuke works too. The windows don't break and the phone still falls.

Edit: even easier way is to grab the phone with the physgun (with the limit disabled) and then press e on the phone. Both methods bugged

theres a little dude in le skybox

People are talking about a radio and dark room, is the dark room the room near the kidz zone with no lights? wheres the radio? I need answers people!