OpenSCAD module for simple gears with round teeth

gear.scad

$fn = 50;
color("yellow")  rotate(90-$t*360/15) gear(4, 10);

module gear(teeth, step, height=8) {
    angle = 360/(teeth*2);
    radius = (step/2) / sin(angle/2);
    apothem = (step/2) / tan(angle/2);
    
    module circles() {
        for (i = [1:teeth])
            rotate(i * angle * 2) translate([radius,0,0]) circle(step/2);
    }
    
    linear_extrude(height) 
    {
        difference() {
            difference() {
                union() {
                    circle(apothem);
                    circles();
                }
                rotate(angle) circles();
            }
            circle (3);
        }
    }
}