Google's has an established tradition of giving users hidden or unexpected surprises. The latest one is currently encouraging millions of users, who may never have heard of them, to shoot "zerglings".
The original idea of the software Easter Egg was that you would come across them unawares. That is often no longer the case and once Google's latest one was discovered it was quickly shared.
To join in this bit of harmless fun all you need to do is to type "Zerg Rush" into the Google Search bar.
As soon as the list of results appears, so does an attack force of red and yellow zeros that start to fall, dissolving the contents of the page as they fall.
The task is to take out as many of the attackers as you can using the cross hair cursor. Once the cursor goes back to being a pointer its too late and the zeros rise up the page to form the message "G G" standing for "Good Game" together with a "Share Score" button to allow you to let other people know how many zerglings you defeated.
What is a "zerg rush"?
A Wikipedia search reveals that is is a tactic in the space strategy game Starcraft and that Zergs are a race of insectoids. Zerglings, therefore are presumably a larval form.
What is in it for Google?
The Easter Egg is only triggered using a Google search. It may therefore encourage users of other search facilities to go back to the Google fold. And, of course, if you want to play competitively or impress your friends the mechanism for this is Google+.