To me it's not a game and not fun at all (I use Tor so I've seen more edge cases than most people). I found CAPTCHA is a school quiz. Some questions are ambiguous and open to interpretation, if it happens, it's not important to select the "correct" answer, but the "expected" answer.
- Select all squares with $object.
If $object only occupies 1/2 or 1/3 of a square, should I select it or not? The "correct" answer is selecting them, but Google marks it as a wrong answer. The "expected" answer is ignoring them.
When using Tor, Google switches the CAPTCHA to the more strict "9 pictures" (or even the "endless pictures with delay on each") version. The rule of "If there is none, click skip" no longer applies. In this version, when Google misidentifies something as the object and you are not selecting it, the answer is wrong because Google thinks you are not selecting all answers. You must guess which one is the misidentified object and select it.
- Select all squares with a traffic light.
If there's a road sign with a picture of traffic light, should I select it or not... Also, sometimes both the big traffic light and a smaller one in the next crosswalk are visible, should I select the smaller one or not? The expected answer is "no", but there are exceptions... Even worse, sometimes there will be 3+ traffic lights spread across a crosswalk, if I select them all, Google marks it as "wrong", sometimes it's unclear which one is the expected answer at all.