Tweening Issue

Unfortunately, the following code does not tween properly as I was hoping it would.

1 - ( ( arc / 2 ) / max( fangle( i - angle ) , 0.001 ) )

I'd like it such that:

if i == angle - arc / 2 || i == angle + arc / 2
	i = 0;
if i == angle
	i = 1;

fangle just fixes angles so GM can use them: for example, -90 becomes 270 and 450 becomes 90.