Very bad game by Mediocre. A complete failure in the opening, underestimated passed pawns and general bad play.
Petir is a much stronger engine than Mediocre, but I had hoped for a bit better play. 16. ... b6 is about as bad as it can get when it comes to greediness and failing to understand the threats of the opponent.
One thing I could learn from this is perhaps try to work a bit with the development section. 3. ... c5 looks very fishy and should be easily avoided with some code discouraging moving the same piece (pawn) multiple times before the other pieces are out.