What you're looking at is the first arena mod :)I needed something simple to use as a pilot, and since oil was mentioned very recently, well...
This is a mod, and not part of the default game at this point. Hence the complete lack of background and other details (but look at that oil on the other hand :D it's so... oily). The mod will be included with the Windows version and be a separate download for Android.
The plan is to add an improved version of this arena in the game itself, but until I find a good place for the inflatable pool thing (e.g. a patio, a basement, something), this will be it.
Oh, and anyone who is potentially interested in creating new arenas - please reach out to me on Discord once v0.9.6 drops, and I'll be happy to assist you :)