fcn make_maze(w = 16, h = 8){
   // make arrays with lists of lists (all mutable)
   vis:=(w.pump(List().write,0)+1)*h + w.pump(List().write,1);
   ver:=(w.pump(List().write,T(Void,"|   ")) + "|")*h + T;
   hor:=(w.pump(List().write,T(Void,"+---")) + "+")*(h + 1);

   fcn(x,y,vis,ver,hor){
      vis[y][x] = 1;

      d:=L(T(x - 1, y), T(x, y + 1), T(x + 1, y), T(x, y - 1)).shuffle();
      foreach xx,yy in (d){
	 if(vis[yy][xx]) continue;
	 if(xx==x) hor[y.max(yy)][x]="+   ";
	 if(yy==y) ver[y][x.max(xx)]="    ";
	 self.fcn(xx,yy,vis,ver,hor);
      }
   }((0).random(w),(0).random(h),vis,ver,hor);
   foreach a,b in (hor.zip(ver)) { println(a.concat(),"\n",b.concat()) }
   return(ver,hor);
}
make_maze();