Without really testing, my estimation is that your stone needs an angle and a decaying speed (in the end, pixelwise, this will be converted to a deltaX and deltaY using sine and cosine) while gravity pulls the stone done, this gravity is then just added or subtracted from the stone's Y coord.
so:
start:
* convert stone angle+speed to deltaX and deltaY (float values!)
* add or sub a gravity amount
* draw stone
* multiply the stone speed with 0.999 or something
loop
Don't have this angle+speed converting formula at hand, it's not difficult tho, but it's probably
deltax=sin(angle)*speed
deltay=cos(angle)*speed
ohwell it probably *is* the fomula anyway.. :P
Perhaps another method is tho change the angle instead of just the y-coord.
so:
start:
* convert stone angle+speed to deltaX and deltaY (float values!)
* add or sub a gravity amount
* draw stone
* multiply the stone speed with 0.999 or something
loop
Don't have this angle+speed converting formula at hand, it's not difficult tho, but it's probably
deltax=sin(angle)*speed
deltay=cos(angle)*speed
ohwell it probably *is* the fomula anyway.. :P
Perhaps another method is tho change the angle instead of just the y-coord.