In your movement system you can change transform.scale.x which will flip your sprite if it’s -1.0.
(Also just a note for the future: you don’t use static variables with bevy, you would instead use a Resource. Or if it’d data attached to a specific entity, you’d make a Component for it)
Teeworlds/DDNet. It has a very simple movement mechanic that is difficult but so satisfying to master, and the skill cap on community maps is crazy