This giant puzzle of a CMYK gradient may be the hardest we've ever seen

Mashable 

Just to let you know, if you buy something featured here, Mashable might earn an affiliate commission. For some, jigsaw puzzles are a slow, relaxing pastime that exercise the creative and logic centers of the mind. If you're one of the former, it's time you experienced Clemens Habicht's 1,000 Colours. This is no ordinary jigsaw puzzle -- because of the subtle changes in color, it's a true test of patience, process, and attention to detail that's not for the faint of heart (or the faint of sight). You won't have the luxury of a real-world image to focus on while you try to match the picture on the box to the jumble of pieces in front of you.