local selectedDG = display.newGroup()
local tilesDG = display.newGroup()

local function animateTile(target)
    -- target.pos gets the position of the selected tile DG so that
    -- we can pull it out of the tilesDG
    local t = tilesDG[target.pos]
    tilesDG.parent:insert(t)
    t.x, t.y = tilesDG:localToContent(t.x, t.y)
    local targetX = selectedDG.numChildren * (t.width + 2)
    local sx, sy = selectedDG:localToContent(targetX, 0)
    transition.moveTo(t , {
        time        = 1500,
        x           = sx,
        y           = sy,
        transition  = easing.outElastic,
        onComplete = function()
            selectedDG:insert(t)
            t.x, t.y = targetX, 0
        end
        })

end

-- touch event listener for the tiles
local function handleTileEvent( event )
    local phase = event.phase
    local target = event.target

    if not target.selected then
        -- do some stuff
    elseif phase == "ended" then
        -- do some game logic stuff
        animateTile(target)
    end
end