that stuff is to fancy for me, i just go with:
let fall=power  //-100, so projectile will go up
let weight=3 Â Â //how fast it falls on y axis
let speed=speed   //how fast it travels on x axis
let grav=grav-weight
let fall=fall-grav
if speed> 10 then let speed=speed-weight //add a speed limit so it doesnt end up taveling in the opposite direction
pushsprite projectile, speed, fall