The "Rocket League 2D" project you're likely referring to is a fan-made physics-based simulation titled Rocket League 2D - 2 Player - Alpha
Here’s a creative piece on the hypothetical chaos of “Rocket League 2D: WTF New.” rocket league 2d wtf new
The "WTF" factor hits in three specific stages: The "Rocket League 2D" project you're likely referring