India, Dec. 1 -- A new optical illusion posted on Reddit has puzzled thousands of users this week, with many calling it one of the hardest animal-spotting challenges they've come across in a long time. The image, shared on the subreddit r/FindTheSniper, shows what looks at first like an ordinary patch of forest. The ground is covered with dried leaves, and thin brown shrubs tangled across the frame. Nothing stands out at first glance. But somewhere inside that cluttered scene, a deer is quietly hiding.

The photo quickly gained traction, mainly because the deer blends almost perfectly into the dry shrubs. The animal's brown coat, dotted with lighter patches, disappears into the background like it was painted into the forest floor itself. ...