Working within the limitations of Vanilla Doom requires authors to be creative with what they got. We have seen things like Back to Saturn X or Doom4Vanilla that all provide a refreshing new experience that still can run within the original MS-DOS exectuable. Doom Zero, the firstborn by author DASI-I, is also such a refreshening new experience that has not seen enough love. DASI-I takes the basic outlines set by id Software and crafts new scenario's around the vanilla limitations. The real brilliance here lies in the details: Using subtle trickery and inventing new mechanics around the confines of the vanilla structures, Doom Zero provides a MegaWAD full of levels that are distinctly different from Doom 2, yet suitably appropiate and natural. They demonstrate a craftmanship for detail and a challenge to anyone looking for a nuanced alternative to the Doom style of gameplay. As such, Doom Zero is a release that has flown under the radar - But which deserves to be played and experienced. It is a striking tribute to Doom's 25th anniversary, and the ''hidden gem'' you are looking for.