At my last job they were constantly asking me to create symbols to represent abstract concepts. They wanted them to be instantly, universally recognizable at 24

At my last job they were constantly asking me to create symbols to represent abstract concepts. They wanted them to be instantly, universally recognizable at 24 pixels by 24 pixels with no text. This is sometimes easy, often impossible. I ended up finding a simple rule of thumb to cut through that work quickly, if I couldn't think of one clear symbol for the concept in 10 seconds then I would never find one that fit all the requirements. I passed that rule on to my project manager and he got a lot better at not making impossible symbol requests.