Just a couple of suggestions, and me being pedantic, but:
1) The 'int main()' line should probably be written as 'int main(int argc, char** argv)'
2) Probably a personal preference, but I'd make sure my window pointer was NULL when it is declared; i.e. 'struct Window *win = NULL'
3) Not as important in this instance, but after the window was closed, I'd reset the win variable to NULL after the window has been closed; i.e. 'win = NULL;'
4) Truth statements should be encapsulated within another set of parenthesis; i.e. 'if(win = OpenWindowTags(NULL,TAG_DONE))' would become if((win = OpenWindowTags(NULL, TAG_DONE))!=NULL) { ... } or if((win = OpenWindowTags(NULL, TAG_DONE))) { ... }.
Always compile with the GCC option -Wall and you'll catch these warnings.
Good idea though. :-)
