It's true that there have always been ways to get the original texture-mapped 3D FPS Doom on your phone - but they usually required some messing about, if not hacking. Happily, thanks to developers SeNSSoft, Doom, or at least 'D00M'(!) is only one tap away, since this is a normal Store install with nothing fancy needed. OK, if you want to go beyond the level packs here and into the official original Doom 'wads' then some file hunting and copying will be needed. But if you're anything like as bad as me at FPS, the free levels and difficulties will be all you'll need.... 

From the Store entry:

Say "Hello" to the Windows Phone port of the legendary first person shooter by the Id Software called "Doom"! This "reincarnation" of the classic PC game is based on the open source implementation called PrBoom but have some unique features.

Trial version has just one limitation - you can play a "FreeDoom" mod only (freeware wad file created by enthusiasts); to play original "Doom" or "Doom 2" wads (or any other PrBoom-compatible mods) you need to purchase a full version of game.

You'll know the game, hopefully, at least if you're over about 35, Doom rewrite the rules of how immersive computer games could be. Here's D00M in action on a Lumia 950:

The traditional five difficulty levels of Doom - you'll want to start off gently while you get the feel of the touch controls....

Happily you can adjust the touch control sensitivity, in case you find yourself lurching around uncontrollably. Or maybe that's just me!

D00M in action. Die, die, die!

There's a map that you can pop up and zoom in on - unfortunately this doesn't help with the puzzles (doors, panels, and so on) - for those you'll need online help.

I wonder what's on the other side of the door?

You can grab D00M here in the Store as a free trial (referring to all the free levels). I'd welcome data points as to how far you get - I must be completely useless as I couldn't even open the very first internal door. Or is this a bug?