Hey hey! I'm minBekker from Germany and I made my own doom clone (classic fps action gam e) from 1999 to 2015.
Much more than 20 non-linear stages in good old mid-nineties-look with lots of crazy enemies, secret passages and an extra load full of Heavy Metal. And best of all: it's completely free!
For more information about the story (and download button), here is the link to the itch.io page: