Draws an arc (part of a circle) based on the turtle heading, turtle position, and inputs.
The center-point of the arc is the turtle's current position.
ARC does not move the turtle.
The arc sweeps an amount given by the
The size (curvature) of the arc is based on the
radius is positive, then the arc starts
radius turtle steps behind the turtle.
radius is negative, then the arc starts
radius turtle steps in front of the turtle.
In both cases, the arc sweeps an angle equal to the
angle is positive, then the arc is drawn in a clockwise direction.
angle is negative, then the arc is drawn in a counter-clockwise direction.
angle is 360 or greater (or -360 or less), then ARC draws a circle.
; a 2D example ARC 360 100 ARC 90 50
; a 3D example PERSPECTIVE REPEAT 36 [RIGHTROLL 10 ARC 90 100]