Thanks for reporting. I guess you are refering to the chess game?
Lets look at line 70: if p0 != p1: window(widget.toplevel).title= "invalid move, ignored." As the compiler told us, there is a symbol window defined in module gtk3 as well as gdk3. So only two possibilities to try. But of course member field "title" told us that this is the gtk window, so fix is if p0 != p1: gtk3.window(widget.toplevel).title= "invalid move, ignored." You have to do 3 more similar fixes, sorry. Another fix would be to modify module import list like import gdk3 exept window Will fix file at github tomorrow -- I wonder why this error has not occured before... And yes, for that window() cast a proc would be fine, no template necessary. But it is some work to fix all that... If you are on Linux you may test the editor as well, it is now available in v 0.3. But you have to install nimsuggest first.