A little while ago, on the Source Modding Community Discord server, with the RTSL mapping Challenges channel, I posted an unofficial weekend challenge. The theme was 3 states of matter: Solid, Liquid and Gas.
The idea was to try to encourage clever and interesting use of those ideas to create puzzles and situations for the player to face.
Unfortunately, only one person sent a map in and this is it.
It’s very short but offers some simple puzzles.