diff --git a/xwall.lua b/xwall.lua
index 5b9f757..fd74198 100644
--- a/xwall.lua
+++ b/xwall.lua
@@ -102,56 +102,35 @@ end
 function xwall.construct_node_box_data(node_box_list, center_node_box_list, node_box_line)
 	local res = {}
 	res.c0, res.c1, res.c2, res.c3, res.c4 = {}, {}, {}, {}, {}
-	local pos0, pos1, pos2, pos3, pos4 = #res.c0, #res.c1, #res.c2, #res.c3, #res.c4
 
-	for i = 1, #node_box_list do
-		local v = node_box_list[i]
-		pos1 = pos1 + 1
-		pos2 = pos2 + 1
-		pos3 = pos3 + 1
-		pos4 = pos4 + 1
-		res.c1[pos1] = v
-		res.c2[pos2] = v
-		res.c3[pos3] = v
-		res.c4[pos4] = v
+	for _, v in pairs(node_box_list) do
+		table.insert(res.c1, v)
+		table.insert(res.c2, v)
+		table.insert(res.c3, v)
+		table.insert(res.c4, v)
 	end
 
-	for i = 1, #node_box_list do
-		local v = node_box_list[i]
-		pos2 = pos2 + 1
-		pos3 = pos3 + 1
-		pos4 = pos4 + 1
-		res.c2[pos2] = {v[3], v[2], v[1], v[6], v[5], v[4]}
-		res.c3[pos3] = {v[3], v[2], v[1], v[6], v[5], v[4]}
-		res.c4[pos4] = {v[3], v[2], v[1], v[6], v[5], v[4]}
+	for _, v in pairs(node_box_list) do
+		table.insert(res.c2, {v[3], v[2], v[1], v[6], v[5], v[4]})
+		table.insert(res.c3, {v[3], v[2], v[1], v[6], v[5], v[4]})
+		table.insert(res.c4, {v[3], v[2], v[1], v[6], v[5], v[4]})
 	end
 
-	for i = 1, #node_box_list do
-		local v = node_box_list[i]
-		pos3 = pos3 + 1
-		pos4 = pos4 + 1
-		res.c3[pos3] = {v[4], v[2], v[3]-.5, v[1], v[5], v[6]-.5}
-		res.c4[pos4] = {v[4], v[2], v[3]-.5, v[1], v[5], v[6]-.5}
+	for _, v in pairs(node_box_list) do
+		table.insert(res.c3, {v[4], v[2], v[3]-0.5,  v[1], v[5], v[6]-0.5})
+		table.insert(res.c4, {v[4], v[2], v[3]-0.5,  v[1], v[5], v[6]-0.5})
 	end
 
-	for i = 1, #node_box_list do
-		local v = node_box_list[i]
-		pos4 = pos4 + 1
-		res.c4[pos4] = {v[3]-.5, v[2], v[4], v[6]-.5, v[5], v[1]}
+	for _, v in pairs(node_box_list) do
+		table.insert(res.c4, {v[3]-0.5, v[2], v[4], v[6]-0.5, v[5], v[1]})
 	end
 
-	for i = 1, #center_node_box_list do
-		local v = center_node_box_list[i]
-		pos0 = pos0 + 1
-		pos1 = pos1 + 1
-		pos2 = pos2 + 1
-		pos3 = pos3 + 1
-		pos4 = pos4 + 1
-		res.c0[pos0] = v
-		res.c1[pos1] = v
-		res.c2[pos2] = v
-		res.c3[pos3] = v
-		res.c4[pos4] = v
+	for _, v in pairs(center_node_box_list) do
+		table.insert(res.c0, v)
+		table.insert(res.c1, v)
+		table.insert(res.c2, v)
+		table.insert(res.c3, v)
+		table.insert(res.c4, v)
 	end	
 
 	if #res.c0 < 1 then res.c0 = nil end