The problem is due to code in "Fixed relation" page.
[code]
if(_isPlaying() && x>xmin+size && y_initialize();
playpause();
}
[/code]

And the following code in the "initialize" page.
[code]
vx=V*Math.cos(angle/90);
vy=V*Math.sin(angle/90);
x=xmin+size2;
y=ymin+size2;
t=0.;
[/code]
When you click "Play" x>xmin and ySo it execute initialize page again.

You can fix it if you modify the code in "Fixed relation" page to.
[code]
if(_isPlaying() && x>[b]xmax[/b]+size && y_initialize();
playpause();
}
[/code]
and the code in initialize page to
[code]
vx=V*Math.cos(angle*Math.PI/180);
vy=V*Math.sin(angle*Math.PI/180);
x=xmin+size2;
y=ymin+size2;
t=0.;
[/code]