change a few things

src/main.lua

@@ -612,12 +612,10 @@ local function VP_moveto(x,z, cx,cz,direction)
     return cx,cz,direction
 end
 local function VP_optimizestack(target)
-    -- go from top to bottom and erase false entries until we encounter a true one.
+    -- go from bottom to top and erase false entries until we encounter a true one.
-    local index = #target
     while #target > 0 do
-        if target[index] then break else
+        if target[1] then break else
-            table.remove(target, index)
+            table.remove(target, 1)
-            index = index - 1
         end
     end
 
@@ -719,7 +717,7 @@ local function VP_printstack(buf, dimensions, cx,cy,cz,direction)
             local tempbuf = buf["stacks"][posasstring(x,z)]
             if tempbuf then
                 cx,cz,direction = VP_moveto(x,z, cx,cz,direction)
-                for _=1,buf["height"],1 do
+                for _=1,#tempbuf,1 do
                     move("down", true)
                 end
                 for _,v in pairs(tempbuf) do