local background = display.newImage( "grass.png" )
 
local radius = 40
 
local xdirection = 1
local ydirection = 1
 
local xspeed = 7.5
local yspeed = 6.4
 
local xpos = display.contentWidth * 0.5
local ypos = display.contentHeight * 0.5
local fruit = display.newImage( "fruit.png", xpos, ypos )
 
-- Get current edges of visible screen (accounting for the areas 
-- cropped by "zoomEven" scaling mode in config.lua)
local screenTop = display.screenOriginY
local screenBottom = display.viewableContentHeight + display.screenOriginY
local screenLeft = display.screenOriginX
local screenRight = display.viewableContentWidth + display.screenOriginX
 
local function animate(event)
        xpos = xpos + ( xspeed * xdirection );
        ypos = ypos + ( yspeed * ydirection );
 
        if ( xpos > screenRight - radius or xpos < screenLeft + radius ) then
                xdirection = xdirection * -1;
        end
        if ( ypos > screenBottom - radius or ypos < screenTop + radius ) then
                ydirection = ydirection * -1;
        end
 
        fruit:translate( xpos - fruit.x, ypos - fruit.y)
end
 
Runtime:addEventListener( "enterFrame", animate );