I'll wait for the update then x)
It's because you do not use delta time. That means it will work fine with 60FPS, if he is using a 120FPS monitor or vsync is disabled it will be faster.
as Luke100000 said, this may be due to a programming quirk with how often the update function is called which I'll try to fix in the new release.
A short-term fix may be setting your monitors refresh rate to 60Hz and seeing if that fixes the issue.
The post-jam version is now live if you wanna check it out ;)
https://pixelcod.itch.io/contra-positive
