Hi, I found this example http://www.angelfire.com/mech/banshee/Grenade.mfa
on daily click for a Grenade (made by a fellow called Sketchy)and it seems to match pretty well the motion that i'm trying to achieve for some particle effects in my game but i'm having difficulty following all the events and math etc

Is there anyone that is able to follow this and would be able to maybe explain to me the principle behind it - even a simplified example would be nice, one that doesn't include any of the aiming and that sort of thing but where i can just input a few values to change distance and angle because i think the whole aiming and strength is whats making it confusing for me to see the principle clearly.

any help would be greatly appreciated - how to make particles that are effected by gravity without using the pinball movement, or particle generator has been eating at me for a while - oh and i'm not really interested in the bouncing just the overall up and down motion really