HL2 Mod with Secrets! | Transmissions: Element 120 (Half-Life 2 Mod)

This Half Life 2 mod has a very interesting, though short, campaign.
The puzzles are challenging, and the secrets are interesting.
Note, it does crash a bit, but if you aren't screen recording, you can fix most of those crashes by looking at the Community Discussions board in Steam at Iazu's post titled "PSA Fixing Some Crashes"
That will send you to a git repo, but if you click on the "Releases" page, you can download a 7Zip pre-built release. Extract it (with 7Zip or WinRar) and run the installer. You will have to tell it where the game is installed. The path will be something like this:
- C:\Program Files (x86)\Steam\steamapps\common\Transmissions Element 120

With that installed, it should crash far less, but use F6 to Quick Save every now and then to avoid having to replay large sections of the game.