Brainstrains: Eye-Popping Puzzles : These challenging and brilliantly colorful puzzles will work out the brain and amaze the eye. Many of the pictures have a trick to fool the puzzler, from vivid optical illusions to 3-D effects that dazzle. Other problems feature a mathematical component â but even before doing the arithmetic, you've got to figure out the logic behind the question. So it's important to look hard and pay close attention. Five bright soccer balls look almost the same. Which ball isn't like the others? A group of bike racers ride across the page in an astounding array. But wait: one of the riders is wearing the wrong number. Hint: the colors of the shirts are the key to the answer.