My first thought when I saw ‘Vacuum cleaner’ was that the answer might be ‘things that require electricity’. It felt like a solid, simple starting point. When ‘Aquarium’ popped up, it seemed to fit perfectly. I was confident enough that I almost typed it in, but decided to wait for a third clue. Then ‘Car engine’ appeared. While many modern engines rely on electrical systems, the core function isn’t purely electrical—it’s mechanical and chemical. The theory was already getting a bit wobbly. By the time ‘Drip coffee maker’ showed up, my initial idea was on life support. While it uses electricity, so do countless other items that weren’t on the list. The pattern felt too broad and ultimately meaningless.
The final clue, ‘Email software (targeting spam)’, was the one that completely destroyed my electrical theory and forced me to start over. I stopped thinking about power sources and started thinking about function. What does a vacuum do? It pulls dirt out of the air. What does an aquarium do? It keeps water clean. The word ‘clean’ and ‘purify’ kept bouncing around in my head. Then it hit me: what component in each of these things performs that cleaning or purifying action? A filter.