If a guy acts really friendly and flirty one day and the next day be very distant towards you when talking to him what does that mean?

well (to the guy) he probably thought you weren't interested in him or you didnt flirt back with him. and it can be that (depending on how long this has been) that he moved on. it's obvious he moved on if you havent flirted with him for like 1-2 weeks

oh but flirt with him more he'll start flirting back as well unless hes one of those guys that just likes to see how many girls would like him or whatever but good luck