include <BOSL2/std.scad> //or screws or threading

/*Original, enhanced by sphere*/
module bob(){
Wo=34;
Lo=60;
Wi=23;
Li=34;
H=10;
Ro = 8;
Ri = 3;
T=1.4;
Off = 2.0;
  
  difference(){
    union(){
      rect_tube(size=[Wo,Lo], wall=(Wo-Wi)/2, rounding=Ro, h=H,irounding=3);
      rect_tube(size=[Wo,Lo-(Wo-Wi)/2], wall=(Wo-Wi)/2, rounding=Ro, h=H,irounding=3);
    }
    rect_tube(size=[Wo-T,Lo-T], wall=(Wo-Wi)/2-T,h=H-T,irounding=3, rounding=Ro);
    rect_tube(size=[Wo-T*2,Lo-T*2], wall=(Wo-Wi)/2-T,h=Off,irounding=3, rounding=Ro); 
    up(Off/2)cuboid([Wo-6*T,Lo-6*T,Off]);
  }
}

module mytext(text){
  mirror([1,0,0]) linear_extrude(1) text(text=text,halign="center");
}

translate([-100,0,0]) {
  translate([0,40]) mytext(text="original");
  bob();
}

translate([0,40]) mytext(text="Minkowski");
union(){
$fn=20;
minkowski(){
  bob();  
  sphere(r=1.5);
}
 }

/* WARNING: Too many unnamed arguments supplied in file ../.local/share/OpenSCAD/libraries/BOSL2/attachments.scad, line 3274
include <constructive-compiled.scad>
translate([100,0,0]) chamfer(4,-2) bob();
*/

/*Approach from 2D*/

a=20;
b=10;
corner=1.5;
module u_shape(){
  difference(){
    square(a);
    translate([a/2-b/2,0]) square(b);
  }
}


module u_round(){
  $fn=30;
  translate([corner,corner])
  difference(){
    offset(r=corner) u_shape();
    offset(r=corner) translate([a/2-b/2+2*corner,3*corner]) square(b-4*corner);
 }
}

module create_by_mirroring(mirroraxis){
  children();
  mirror(mirroraxis) children();
}

//mpo();
len=200;
wid=100;

translate([0,len/1.5]) mytext(text="2D extrude");
create_by_mirroring([0,1,0]) create_by_mirroring([1,0,0])
translate([wid/2,len/2,0]) union(){
/*right side*/
rotate([90,0,0]) linear_extrude(len) u_round();
/*top right edge*/                                   
rotate_extrude(angle=90) u_round();
 /*top side*/
translate([-wid,0,0]) rotate([0,0,90]) rotate([90,0,0]) linear_extrude(wid) u_round();
translate([-wid,0,0]) rotate([0,0,90] ) rotate_extrude(angle=90) u_round();
}

#translate([a,0]) u_round();