Three hits, and the ring tells you
Every O has a ring around it that thins as you land clicks. Two hits in and it is nearly gone, which is exactly the information that makes you stay on one target while four others quietly finish off your knowledge panel.
They go for whatever is nearest. Big result blocks take the longest to chew, so the chips and the tab row usually disappear first and you never see it happen.
APM is the real score
Kills is the obvious number. Actions per minute is the one people compare, borrowed straight from strategy games, and if you are above 120 your hand will let you know about it in the morning.
Then it spells GG
When the last block goes the survivors stop hunting, drift into the middle and arrange themselves into two letters. No score screen, no retry prompt. Just GG and an empty frame.
Removed, and still searched for
It shipped as a live search feature in 2012 and was retired later, which is why zerg rush removed and zerg rush easter egg removed are still typed in weekly. The name is from strategy games, where rushing means swamping someone before they can build a defence.
Spelling is a disaster area: zarg rush, zerf rush, zerg ras, zury rush, zergrush, zerg berg. Some people run it inside google mirror for a reversed round, which ruins your aim on purpose. If you want a swarm you can actually beat, the wall in google block breaker at least ends.