Rolling rock is unkillable object that move on floor and fall if no floor under object.
iXD is speed of horizontal movement. When object fall, iXD set to 0.
If iXD is 0, first value of iXD is 4.
iYD is speed of vertical movement. When object fall, iYD increase by 2 at each cycle with maximum 12.
|0||14||24||image diplay when rock fall|
|1||14||25||image diplay when rock roll|
|2||14||26||image diplay when rock roll|
|3||14||27||image diplay when rock roll|
When rock fall if iXD is not 0, move object horizontally.
When Rolling rocks hit block, set iXD to 0 first. Next cycle set to 4 or -4.