Sonic Robo Blast 2 is a free 3D Sonic the Hedgehog fan-game built on a heavily modified fork of the Doom Legacy source port of Doom. It is closely inspired by the original Sonic games from the Sega Genesis, and attempts to recreate their classic design in 3D with robust multiplayer and mod support.
Online multiplayer gameplay snippet of Match mode in Tidal Palace Zone - flying about and shooting stuff before retreating and jumping through a ring box to collect more rings. My aiming is pretty awful here.
Please note the yellow "Get / Send / Gamemiss / Sysmiss" text is not part of the normal HUD - it's network statistic information that I choose to have displayed when running a server (via "netstat 1" in console). I merely forgot to turn it off before recording, so just ignore it.