-- compute angle between two sets of points
local function angleBetweenPoints ( srcObjx, srcObjy, dstObjx, dstObjy )
        -- make sure we never return -1.#IND if we try to find angle between identical points
        if ( srcObjx == dstObjx and srcObjy == srcObjy ) then return 0 end
 
        -- Original angleBetween
        local xDist = dstObjx - srcObjx ; local yDist = dstObjy - srcObjy
        local angleBetween = math.deg( math.atan( yDist / xDist ) )
        if ( srcObjx < dstObjx ) then angleBetween = angleBetween + 90 else angleBetween = angleBetween - 90 end
 
        -- These tend to get flipped around, this is a quick fix
        if ( angleBetween == 0 ) then angleBetween = -180
        elseif ( angleBetween == -180 ) then angleBetween = 0
        end
        return angleBetween
end
 
-- display the circle
local circle = display.newImageRect( "circle.png", 256, 256 )
circle.x = display.contentWidth / 2
circle.y = display.contentHeight / 2
 
-- what to do when circle is touched
local function accessCircle( event )
        local t = event.target
 
        -- is the circle being touched?
        if event.phase == "began" then
 
                -- keep touch focus on the circle
                local parent = t.parent
                parent:insert( t )
                display.getCurrentStage():setFocus( t )
                t.isFocus = true
 
                -- store initial angle
                t.angle0 = t.rotation
 
        elseif t.isFocus then
                -- is finger moving around circle?
                if event.phase == "moved" then
                        t.x1 = event.x
                        t.y1 = event.y
                        local newAngle = math.ceil( angleBetweenPoints ( t.x, t.y, t.x1, t.y1 ))
                        -- rotate circle based on original angle (use t.rotation = newAngle for direct angle)
                        t.rotation = t.angle0 + newAngle
 
                -- did finger let go of circle?
                elseif event.phase == "ended" or event.phase == "cancelled" then
                        -- release focus for other objects
                        display.getCurrentStage():setFocus( nil )
                        t.isFocus = false
                end
        end
end
 
-- let circle object listen for touch events
circle:addEventListener( "touch", accessCircle )