diff --git a/utils/formspec.lua b/utils/formspec.lua
new file mode 100644
index 0000000..57a7156
--- /dev/null
+++ b/utils/formspec.lua
@@ -0,0 +1,38 @@
+function generate(size)
+	if size == "small" then
+		cfg = {
+			window_width = 8,
+			window_height = 9,
+			chest_width = 8,
+			chest_height = 4,
+		}
+	elseif size == "big" then
+		cfg = {
+			window_width = 14,
+			window_height = 10,
+			chest_width = 14,
+			chest_height = 5,
+		}
+  end
+  -- calc padding to vertically align center the chest and the player's inventory
+  local player_inv_y_orig = cfg.chest_height + 0.85
+  local player_inv_x_orig = (cfg.window_width - 8) / 2 -- 8=player_inv_width
+	return "size[" ..
+    cfg.window_width .. "," .. cfg.window_height .. "]" ..
+  	default.gui_bg ..
+  	default.gui_bg_img ..
+  	default.gui_slots ..
+  	"list[current_name;main;0,0.3;" ..
+    cfg.chest_width .. "," .. cfg.chest_height .. ";]" ..
+  	"list[current_player;main;" ..
+    player_inv_x_orig .. "," .. player_inv_y_orig ..
+    ";8,1;]" ..
+  	"list[current_player;main;" ..
+    player_inv_x_orig .. "," .. (player_inv_y_orig + 1.15) ..
+    ";8,3;8]" ..
+  	"listring[current_name;main]" ..
+  	"listring[current_player;main]" ..
+  	default.get_hotbar_bg(player_inv_x_orig, player_inv_y_orig)
+end
+
+return generate