After initially being presented with two options, simple and advanced, seeing as I've made no maps since clumsy half-attempts to get to grips with BUILD, I play smart and go Simple to start.
I find that I can place blocks, I can rotate them too, but...that's all. I saw the easy-peasy diagram at the start (it's a great KISS control scheme) but single presses of the middle mouse button (which it showed controlled the height pieces are placed at) is having no effect. Push and hold/scroll - nothing either. The cursor doesn't stay put!
Now what? ok. There are little "R" and "P" labels on the buttons, so let's try that (this is after about three quit/reloads of the editor, already.)...No. (tried all methods mentioned at least once, prior, and post placement of the pieces)
It would take me another couple or so cycles to realise that the picture meant the mouse scroll WHEEL!
Suggested solution: Could we please, improve that instructions image by adding the word "Scroll" in the appropriate place? I think the Simple setting would be all the easier, and better for it. Also, can anybody explain what the R's and P's on the tile buttons actually indicate, or correspond to?
The current eraser icon looks like a footprint. Consider adding a tooltip, and/or moving it in line with the existing tools (tiles), so that it's with related items, not in a seperate utilities area of the interface. I didn't realise that the little camera icon, once blue, is the way you manually adjust your view of the map, at 360 degree rotation. Please, add that detail to the starting diagram - or, include a label/tooltip in the interface.
Consider enhancing delete key in functionality, to a universal eraser shortcut. At this time, it seems it can only be used in such a way, provided that the cursor is at a matching height/level to the piece you want to delete.
As a closing point, I didn't find it helpful how when I did run into difficulty, the Escape key, instead of offering any kind of summary, or text to help in any way, only presented the option to quit the editor. Perhaps you could add in there a hyperlink to a SM editing subforum.