This is one of my top 10 apps ever. Highly recommended for any first person shooter fans or for a streak of nostalgia. Although a bit vanilla due to public domain art the mechanics are spot on and with the downloadable level packs (free) there is a ton of content, including award winning Doom add-on levels. I am still hopeful the developer adds downloadable alternative monsters/weapons. This was an insane steal at $0.99 and anyone who doesn't grab it free should resign in their Touch Arcade username.