diff --git a/maps/includes/base.lua b/maps/includes/base.lua
index c73e3f9..59a3e36 100644
--- a/maps/includes/base.lua
+++ b/maps/includes/base.lua
@@ -8,6 +8,7 @@
 -----------------------------------------------------------------------------
 
 Class = require "util.class"
+Collection = require "util.collection"
 
 -----------------------------------------------------------------------------
 -- defines
diff --git a/maps/includes/util/collection.lua b/maps/includes/util/collection.lua
new file mode 100644
index 0000000..5a3cb31
--- /dev/null
+++ b/maps/includes/util/collection.lua
@@ -0,0 +1,119 @@
+-- backwards compatibility for the Collection class
+
+local Class = require "util.class"
+
+local function setup_items_key(self)
+	-- keep a usable reference to the base metatable
+	local real_obj = setmetatable({}, getmetatable(self))
+	-- add special handling of the items key
+	setmetatable(self, {
+		-- the items key returns an iterator
+		__index = function(t, k)
+			if k == "items" then
+				local i = 0
+				local n = self:Count()
+				return function()
+					i = i + 1
+					if i <= n then return self.entities[i] end
+				end
+			end
+			return real_obj[k]
+		end,
+		-- protect the items key from being assigned
+		__newindex = function(t, k, v)
+			if k == "items" then
+				return
+			end
+			real_obj[k] = v
+		end
+	})
+end
+
+local Collection = Class(function(self)
+	setup_items_key(self)
+	self.entities = {}
+end)
+
+
+local function get_param_as_table(param)
+	if param == nil then return {} end
+	if type(param) == "table" then return param end
+	return {param}
+end
+
+-- lua tables start at index 1
+local function to_lua_index(collection_index)
+	return collection_index+1
+end
+
+-- Collection started at index 0
+local function to_collection_index(lua_index)
+	return lua_index-1
+end
+
+function Collection:AddItem(entity_or_entities)
+	local entities_to_add = get_param_as_table(entity_or_entities)
+
+	for i,entity_to_add in ipairs(entities_to_add) do
+		table.insert(self.entities, entity_to_add)
+	end
+end
+
+function Collection:RemoveItem(entity_or_entities)
+	local entities_to_find = get_param_as_table(entity_or_entities)
+
+	for i,entity_to_find in ipairs(entities_to_find) do
+		local i = self:FindItemIndex(entity_to_find)
+		if i then
+			table.remove(self.entities, to_lua_index(i))
+		end
+	end
+end
+
+function Collection:RemoveAllItems()
+	for k in ipairs(self.entities) do
+		self.entities[k] = nil
+	end
+end
+
+function Collection:Count()
+	return #self.entities
+end
+
+function Collection:HasItem(entity_or_entities)
+	local entities_to_find = get_param_as_table(entity_or_entities)
+
+	for i,entity_to_find in ipairs(entities_to_find) do
+		if self:FindItemIndex(entity_to_find) then
+			return true
+		end
+	end
+	return false
+end
+
+-- this is a strange function
+function Collection:GetItem(entity_or_entities)
+	local entities_to_find = get_param_as_table(entity_or_entities)
+
+	for i,entity_to_find in ipairs(entities_to_find) do
+		local i = self:FindItemIndex(entity_to_find)
+		if i then
+			return self:Element(i)
+		end
+	end
+end
+
+function Collection:FindItemIndex(entity_to_find)
+	for i,entity in ipairs(self.entities) do
+		if entity:GetId() == entity_to_find:GetId() then
+			return to_collection_index(i)
+		end
+	end
+	return nil
+end
+
+function Collection:Element(i)
+	return self.entities[to_lua_index(i)]
+end
+
+return Collection
\ No newline at end of file