world.entities = {
        ["enemies"] = {group = "enemies"},
        ["pickups"] = {group = "pickups"},
        ["portals"] = {group = "portals"},
        ["crates"] = {group = "crates"},
        ["traps"] = {group = "traps"},
        ["checkpoints"] = {group = "checkpoints"},
        ["springs"] = {group = "springs"},
        ["bumpers"] = {group = "bumpers"},
        ["platforms"] = {group = "platforms"},
        ["props"] = {group = "props"},
        ["decals"] = {group = "decals"},
        ["materials"] = {group = "materials"}
    }

    for i, type in pairs(world.entities) do
        print (type.group)
    end

--[[ loops in wrong order ?
portals
springs
enemies
materials
decals
bumpers
crates
platforms
props
checkpoints
pickups
traps
--]]