Flooded Pits

local Mod = RegisterMod("FloodedPits", 1);
local game = Game()

function Mod:onPits()

	local level = game:GetLevel()
	local room = level:GetCurrentRoom()
	local backdrop = room:GetBackdropType()

	if CurRoom ~= level:GetCurrentRoomIndex() or CurStage ~= level:GetStage() then
		-- new room
		RoomConfig = {}
		for i = 1, room:GetGridSize() do
			local Grid = room:GetGridEntity(i)
			if Grid == nil then
				RoomConfig[i] = nil
			else
				RoomConfig[i] = {Type = Grid.Desc.Type, Variant = Grid.Desc.Variant, State = Grid.Desc.State}

			end
		end
	end
	CurRoom = level:GetCurrentRoomIndex()
	CurStage = level:GetStage()

	-- check for chances
	for i = 1, room:GetGridSize() do
		local Grid = room:GetGridEntity(i)
		if Grid then
			if Grid.Desc.Type == GridEntityType.GRID_PIT then
				-- your code
				if level:GetStageType() == StageType.STAGETYPE_AFTERBIRTH
				or backdrop == 6 then
					local sprite = Grid.Sprite
					sprite:ReplaceSpritesheet(0, "gfx/grid/custom/grid_pit_water_drownedcaves.png") -- place here your png file
					Grid.Sprite = sprite
					Isaac.ConsoleOutput("Water!!")
				end
			end
		end
		-- general code
		-- if Grid and RoomConfig[i] and
		-- (Grid.Desc.Type ~= RoomConfig[i].Type
			-- or Grid.Desc.Variant ~= RoomConfig[i].Variant
			-- or Grid.Desc.State ~= RoomConfig[i].State)
		-- then
			-- Isaac.ConsoleOutput("Ok")
			-- specific grid modifications
			-- if RoomConfig[i].Type == GridEntityType.GRID_PIT
			-- and RoomConfig[i].State == 1
			-- then
				-- your code
			-- end
		-- end
		if Grid then
			RoomConfig[i] = {	Type=Grid.Desc.Type,
						Variant=Grid.Desc.Variant,
						State=Grid.Desc.State,
					}
		else
			RoomConfig[i] = nil
		end
	end
end
-- Mod:AddCallback(ModCallbacks.MC_POST_UPDATE, Mod.onPits)
Mod:AddCallback(ModCallbacks.MC_POST_NEW_ROOM, Mod.onPits)