This puzzle is based on the "connecting wall" from the British tv show "Only Connect". The goal is to group the 16 words into 4 groups of 4 words that all share a property. Here are the words:
| MIX | LASER | RACECAR | EMPTY |
| SONAR | SCUBA | NOON | VIM |
| MOSSY | KAYAK | LIVID | BOOST |
| CIVIL | ROTATOR | CAPTCHA | BIOPSY |
What are the four groups of words?What is the connection between the words in each group?