Batman: Gotham by Gaslight is a 2018 American animated steampunk superhero film produced by Warner Bros. Animation and distributed by Warner Bros. Home Entertainment, featuring an alternate version of the DC Comics character Batman. It is the thirtieth film in the DC Universe Animated Original Movies series. It is directed and produced by Sam Liu and written by James Krieg, loosely based on the one-shot graphic novel of the same name by Brian Augustyn and Mike Mignola. (wiki)
Batman: Gotham by Gaslight, originally published in 1989, is considered to be DC Comics’ first Elseworlds story. “In ELSEWORLDS, heroes are taken from their usual settings and put into strange times and places–some that have existed, and others that can’t, couldn’t or shouldn’t exist.” – DC editorial copy.