One of the best renditions of this was when I was using the sounds from the Atmosfear mod for STALKER, and all the mods that use it. This was only on my end though.

The fog required a lot of precise timing and entity inputs to look good. As for the most tedious entity I/O in the map, it probably was the lightning rod when a lightning bolt hits it. The end result was great though.

jb_airship is probably one of the better maps I've made. The whole layout took under a year, but I kept touching it up over time. The idea to make the fog roll in was there from the beginning and uses several tricks to achieve the effect seen in-game.

When the player changes to another time period, entities in the previous time period stay "paused" and cannot be interacted with. When switching back to the previous time period, they will now resume from where they left off. There is currently a bug where they will drop items in a seperate time.

Tweaking collision to work with time travel. Originally it would only read the present time period. Now it takes the current time period into account.

Update: got it working with saves

I had to change a considerable amount compared to standard Quake to get this to work. Also, there are some bugs still like enemies not spotting me immediately. They can also cross time-periods which may or may not be useful as a mechanic.

There's a ton to iron out, but this is what I have so far for a Quake-derived game. Note that I'm using LibreQuake in place of the ID assets.

The biggest thing so far is being able to switch between three loaded BSPs at runtime as a time travel gimmick.

Black Mesa Skateboarding Team

"Here, let's try this."

me when i feel a spider on me at night