Camera offsetting

local physics = require("physics")
    physics.start(); physics.pause()

    local _W = display.contentWidth
    local _H = display.contentHeight

    -- used to change the scale as needed
    local myScale = 1

    local group = display.newGroup()

    -- set the scale of the group
    group.xScale = myScale
    group.yScale = myScale

    -- create a moving object for the sample
    local ship = display.newCircle(60, 60, 60)
    ship.x = 100
    ship.y = 100
    physics.addBody(ship, 'dynamic')
    group:insert(ship)

    -- create a lister so we can touch the ball to move it
    ship.myTouchListener = function(event)

            if event.phase == 'began' then
                event.target:setLinearVelocity(400, 0)
            end

        --phases(began, moved, ended)
        end

    ship:addEventListener( "touch", ship.myTouchListener )




    -- create ground for context
    for i = 1,100 do
        --local myRectangle[i] = {}

        local myRectangle = display.newRect(group, 50*i, _H - 100, 100, 100)
        myRectangle:setFillColor(math.random(100, 255), math.random(100, 255), math.random(100, 255), 255)

        physics.addBody(myRectangle, 'static')
    end



    -- todo:
    -- this is the function that needs tweaking to slide the screen back depending
    -- on which direction we move
    local screenCenter   = display.contentWidth / 2
    local offset         = 0
    local camChangeSpeed = 1
    local function moveCamera()

        -- check which way the ball is moving
        local myX, myY = ship:getLinearVelocity() --if ship.ve

        -- Find limit by speed
        local desiredOffset = myX / 4
        if desiredOffset < offset then     offset = math.max( offset - camChangeSpeed, desiredOffset )
        elseif desiredOffset > offset then offset = math.min( offset + camChangeSpeed, desiredOffset ) ; end

        group.x = -ship.x + screenCenter - offset
    end

    -- move the group as the ship moves
    Runtime:addEventListener('enterFrame', moveCamera)

    -- begin the physics
    physics.start();