Hi Net :) thanks
I figure out something but kind of weird.. :D
Like you say new touch gets new id +1 each time.
since I do this stuff on laptop and my laptop screen is not touch screen, when I try the intermediate template like Touch Zooming, the ID only blink between 0 and -1
But when I try to export it to .APK and run it on phone (with touchscreen), I saw touchID keep increasing in every touch.
and yes.. i am thinking to make the grey box (sprite) separately become 2 different sprite object
then use "on touch object [ ]" to indentified the touchID and save it in certain variable