I'm guessing it's line 113:
if (e.touches.length == 4) targets[0].alive = false;
So if you 4-finger touch the screen it automatically kills the first target, is that it? I couldn't get that to work.
Unfortunately there are many mistakes, both in the text and in the sample code.
Also, as @kirilloid said, it just explains the mechanics but does not give examples of problems that this solves.
@jbucaran - hello! :-)
Picodom, Ultradom, Superfine.. I'm getting dizzy trying to keep up with the name changes ;-) Have you settled on the name now?
thanks, foxdonut