I don't remember any specific similarities to Laputa, both have airships (although Laputa doesn't have Zeppelins) but that's about it. Been a while since I had a good go though.
I decided to Wikipedia it since I remember it being related.
"Japanese video game developer HOT-B began work on a video game adaptation of Laputa. The final product, released in Japan as Koutetsu Teikoku for the Sega Mega Drive video game console as a shoot 'em up, is very different to the source material. Some similarities with the film can be seen, in the aesthetic steampunk-esque designs of the game. The game was subsequently brought to western market in 1992 by Acclaim Entertainment's label Flying Edge under the title Empire of Steel in Europe and Steel Empire in the United States.[12]"