How do i make the player's character rotate to the mouse? [closed]

So, i am trying to make an attack system where the player throws a rock in a certain direction. However, i think it looks goofy when the player throws forwards but the projectile goes backwards.

What i'm trying to do is make the players' character rotate towards the current position of the mouse. But i have no idea how to do that.

(The game that i'm making is in R15, so if you're about to post a line of code, please make it R15 compatible.)