As we can read in Wikipedia, Gotham by Gaslight is a DC Comics one-shot comic, considered to be the first Elseworlds story, where DC Comics heroes are taken out of their usual setting and put into alternate timelines or realities. In Gotham by Gaslight, Batman is set in 1889, in a sort of steampunk europe.
A game based on Gotham by Gaslight was pitched by Day 1 Studios, and an early prototype was created. Some menù concept arts are and a video of the proto are saved in below, to preserve its existence. Thanks to Supererogatory and MitsuharuSan for the contributions!