Things about ultrakill that I found interesting. Some facts have been recorded before patch 15 so let me know if something has changed.
0:00 - Intro, funny stuff on 4-4
1:40 - Railgun interactions
2:00 - Sisyphus proves he was a drill all along
2:07 - S.R.S. Cannonball stuff
2:56 - Disappearing falling effects
3:06 - Freezing enemies in place
3:20 - Ghost Drones
3:56 - Sawblade launcher stuff
4:09 - Magnet Interactions
4:40 - Firestarter stuff
4:54 - Sawed-On Shotgun stuff
5:12 - Alt Shotgun tech
5:25 - Puppeted + Sandified
5:42 - Disabling Clash mode in 4-S
6:07 - Reflecting projectiles with the Knuckleblaster
6:11 - Outro
The music in the video is from 5-S, if you're wondering
ULTRAKILL is a game by Arsi "Hakita" Patala. The background music is part of the ULTRAKILL OST.