Ready for a visual challenge that will put your observation skills to the test? At first glance, these two cartoon-style images look exactly the same—a smiling woman snapping a selfie in front of Big Ben, coffee in hand.

But if you look closer, you’ll find 15 subtle differences between the two. They’ve driven thousands of puzzle lovers up the wall.

Start By Observing Carefully

Before diving in, take a moment to study both images. This isn’t a race—success here is all about focus and careful observation.

Use your finger or a pen to track what you find—you might be surprised by how much your mind fills in automatically without realizing.