What is "AoTTG?"
The Attack on Titan Tribute Game is a free-to-play, singleplayer and multiplayer Unity game published in 2013 by the indie game developer known as "Fenglee". It received updates for the next three years. The final stable build was released on January 4th, 2015 (version "01042015"), and the last beta build was released on December 26th, 2016 (version "12262016").
As of January 12th, 2023, the original game servers and website are unavailable. However, community-ran efforts have kept the game alive and well since then.