module min_lines(D) {
    divisor = 60;
    len=D/20;
    Dist=D-len;
    for(dot=[0:6:360]){
        translate([sin(dot)*Dist,cos(dot)*Dist,0])
        color("black")
        rotate([0,0,-dot]) // negative z rotates towards outer circle
        if (dot % 90 == 0){ 
            divisor = 30;
            translate([0,-0.3,0])
            square([D/divisor,D/divisor*3], center=false);
        }
        else { 
            divisor = 60;
            square([D/divisor,D/divisor*3], center=false);
        }
    }
}

min_lines(16);