-- vars
local balls = {}
local mW,mH = display.contentWidth*0.5, display.contentHeight*0.5
-- physics
local physics = require "physics"; physics.start()
physics.setGravity( 0, 0 ); physics.setDrawMode( "hybrid" )
 
-- FUNCTIONS
local function placeBall( anglePerBall, ballspeed )
        balls[#balls+1] = display.newCircle( mW, mH-50, 20 )    
        balls[#balls].yReference = 50
        balls[#balls]:rotate( anglePerBall )
        physics.addBody( balls[#balls], "dynamic", {  isSensor = true, radius = 20 } )
        balls[#balls].id = #balls
        balls[#balls].delta = ballspeed         
end
 
 
local function mainLoop()
        for i=1,#balls do
                balls[i]:rotate(balls[i].delta)         
        end
end
 
local function onGlobalCollision( event )
        if ( event.phase == "began" ) then
                print( "Global report: " .. event.object1.id .. " & " .. event.object2.id .. " collision began" )
        end
        -- MY PROBLEM
        -- print only once on terminal if "began" / never print if "ended"
        -- anyway don't laucnh when balls collisions ...
end
 
-- GO
for i=1,2 do
        placeBallWithJoint( i*90, i*3 )
end
Runtime:addEventListener("enterFrame", mainLoop)
Runtime:addEventListener( "collision", onGlobalCollision )