Ending on May 12th, an offer on Steam lets you play Wolfenstein: The Old Blood for free if you pre-purchase idSoftware's DOOM that comes out on May 13th. Having Very Positive rating on Steam, Wolfenstein: The Old Blood is a standalone prequel to the critically acclaimed first-person action-adventure shooter, Wolfenstein: The New Order. The offer is a great shot if you are planning to play DOOM anyway. Being a shooter fan, you will probably like Wolfenstein: The Old Blood as it does retain the feel of The New Order while bringing something new. Lastly, The Old Blood will be a good time killer before DOOM comes out.