Could use more of a tutorial - took me until the middle of the second island before I figured out you could right-click to erase pieces or stop adding new pieces.
Some kind of navigation system would help -- I see radar mentioned a few times, a coordinate system would be good too especially since we seem to be on a grid.
There should be a "Are you sure you want to retreat?" dialogue box -- there were a few times when I meant to click on "rest" and clicked "retreat" by accident. That annoys me a lot.