do the second thing FRA32 said, it worked for me when I made a terrible mistake, I got a box and put this in it's update box and saved it:(e)=>{quit} and I sould of put it in post step
and for the movement script you can do
onCollide = (e)=>{CanJump = 1}
PostStep = (e)=>{KeyIsDown "up" ? {CanJump == 1 ? {vel = [(Whatever velocity up is)];CanJump = 0} :{}} : {}}