Group for Physics 2

local mt = {}
function mt.__newindex(t, key, value)
    if key == 'X' or key == 'Y' then
        local lkey = key:lower()
        for i = 1, t.numChildren do
            if not t[i][key] then
                t[i][key] = t[i][lkey]
            end
            t[i][lkey] = t[i][key] + value
        end
    end
    t[key] = value
end
setmetatable(frontgroup, mt)