difference()
{
    minkowski()
        {
        translate([0,0,10]) cube([40,12,90], center=true);
        sphere(3);
        }
 
    translate ([10,4,-34]) cylinder(h=68, r=9);
    translate ([-10,4,-34]) cylinder(h=68, r=9);

    translate ([1,5,-34]) cube([18,6,68]);
     translate ([-19,5,-34]) cube([18,6,68]);

     translate ([-18,-8,36]) cube([36,18,18]);

    translate ([-20,8,-46]) cube([40,1,100]);

}

it could do with me using variables of course but its a start.
i think I find this more intuitive in a way than struggling with a GUI and having to enter values manually anyway.

I bought my SD2 mainly for one purpose, to make parts for a line of a new style of clock.  (more on that as the progress... progresses)  Most of all, I am making short cylinders, with 60 holes for LEDS.

I started off - as recommended with Google SU8.  it's awesome indeed, yet not quite right for me.  While I could set up macros to do A LOT of repetitive tasks,  like making 60 holes in a cylinder, anytime I wanted to make a change in size of the LEDs or the cylinders' , I'd have to do a lot of editing, rather than a simple scaling command to change what I want and ignore what I don't.

I saw many things on thingiverse.com that were "parametric" -sounds like something i could use- and noticed most had one thing in common, SCAD files...

So I downloaded and installed it. Did about 15 minutes of reading and playing with some examples, and starting designing in earnest.  Once I got it, I GOT IT! 

You define the parts that make up your shape with commands and formulas.  Then you can join (union) or subtract (difference) shapes just by listing them after the "parent" shape. 

45 minutes later, I had not just my cylinder, 60 holes and all, but I also built it parametric, so I can change the diameter, height, or thickness of the cylinder, and the holes snap into place, or I can change the size of the holes, without affecting anything else, all by changing a variable or 2.

From starting the download to a first completed, workable, parametric part, in under an hour, shows just how easy SCAD is to use.  If you have any programming prowess whatsoever, you will take to this like a duck to water.

I know it's not for all design work, but it does do a few things, easily, that many of the visual-based programs can't do, or are a pain in the butt to do.

check it out:  openscad.org