Played with this a little. Note that you can go to https://web-cad.org/?your-local-file-name-here to save models as you go in your local browser storage by file name that you create; it’s all running in the browser.
The constraint sketching is pretty easy. I had two problems: First, I couldn’t constrain a point to the origin; second, I couldn’t figure out how to exit the sketch to extrude on the model. I ended up hitting save, closing the tab, and re-opening it.
I was able to set length equality on multiple lines at once, I didn’t have to do it in pairs.
I tried to constrain multiple points to an arc by selecting all the points and the arc and then constrain points to arc, but that failed. When it failed, it didn’t tell me it failed, it just didn’t do anything. So I had to do that one set at a time.
Unlike FreeCAD, it doesn’t seem to indicate full constraint in any way I noticed, beyond no longer being able to manipulate the sketch.
I made a construction circle circumscribing the hexagon to make it regular:
But when I extruded,
the construction circle was extruded:
Putting a fillet on the outer circle made it clear that both the construction and model geometry were extruded together:
It’s pretty neat as far as it goes, but still some quirks I think. 
I like the idea of a click-and-drag alternative to CascadeStudio — sometimes I want to write code, sometimes I don’t!
Thanks for the nice review. This is a program I found years ago and had forgotten about. I looked to see if I had posted it before and I had but it was back in the G+ days and on the K40 section.
There are times that it’s nice to be able to do a quick sketch without all the bother of some of the other overhead that the bigger programs have.
I’m glad you enjoyed playing with it.