Detetcting two buttons pressed simultaneously

Hello guys, I’m trying to make my app recognise when I press two buttons simultaneously. That’s the code I have written: 

----------------------------------------------------------------------------------------- -- -- main.lua -- ----------------------------------------------------------------------------------------- local a = display.newCircle( 100, 100, 25 ) a:setFillColor(1, 0, 0) local b = display.newCircle( 200, 100, 25 ) b:setFillColor(0, 0, 1) local flag1=0 local flag2=0 system.activate( "multitouch" ) local function tap1(e)   if e.phase=="began" then     flag1=1   end end local function tap2(e)   if e.phase=="began" then     flag2=1   end end local function check()   if flag1==1 and flag2==1 then     local c=display.newCircle(150, 200 , 25)     c:setFillColor(0, 1, 0)     flag1=0     flag2=0   elseif flag1==1 and flag2==0 then     local c=display.newCircle(150, 200 , 25)     c:setFillColor(1, 0, 0)     flag1=0     flag2=0   elseif flag1==0 and flag2==1 then     local c=display.newCircle(150, 200 , 25)     c:setFillColor(0, 0, 1)     flag1=0     flag2=0   else     local c=display.newCircle(150, 200 , 25)     c:setFillColor(1, 1, 1)     flag1=0     flag2=0   end   return true end a:addEventListener("touch", tap1) b:addEventListener("touch", tap2) Runtime:addEventListener("enterFrame", check)

The problem is: I need to be really precise in touching both at the same time or it won’t be detected as multitouch. How can I fix this? I want the multitouch to be more “tolerant” on pressing timing. Hope I explained the problem properly