Homing-attack, spin-dash and ring-scatter through Hell as the real Sonic from your own Sonic Adventure 2.
Play ULTRAKILL's levels as the real Sonic from your own copy of Sonic Adventure 2, in third person.
Pure Sonic, no guns
Press T to switch between Sonic and V1 at any time. Some doors and switches need V1's arsenal, so swap to V1, shoot what you need, then press T again to get back to Sonic. He keeps his rings.
Rings are your health. Demons burst into SA2's gold rings when they die, spinning just like in SA2. Get hit while you're holding rings and they scatter, so grab them back. Get hit with none and you're done.
Straight from your SA2
An SA2-style SCORE / TIME / RINGS counter sits next to ULTRAKILL's style meter, and Sonic's moves score style.
Settings (ULTRAKILL/BepInEx/config/melty.sonickill.cfg): SwitchKey (T), SonicHeight, CameraDistance, RunSpeed, SA2Music.
Single player. Needs ULTRAKILL and Sonic Adventure 2 (both Steam). Melty installs BepInEx and points the mod at your SA2 folder.