Sonic Robo Blast 2

Sonic Robo Blast 2 is a 1998 platform game created by Sonic Team Junior. It is a fan-made Sonic the Hedgehog game based on the engine of Doom. It is one of the oldest Sonic fangames still being updated, with Update 2.2 releasing in 2020. It features Sonic, Tails, and Knuckles attempting to stop Dr. Eggman from using the Black Rock to take over the world. The game has been well received for its gameplay, music, and graphics. 
The game has an active modding community, and also has a fan-made spinoff, called Sonic Robo Blast 2 Kart, which is a racing game similar to Super Mario Kart.