interesting game! it didn't make me think of a captcha - it made me think of the game Set! then i wondered if additional challenges could be:
- finding identical pairs within a sea of unique shapes, each with different colors and patterns (it wouldn't comply with the 'one too many' theme, though. more like TWO too many!)
- looking for shapes that are literally shapeshifting - changing color or shape or pattern. maybe there's a target shape (like a blue button with two holes), and all the shapes keep changing. you have to click on one when it matches the target. (could be very intense!)
anyway, good work! with a few variations, I think it could be a really fun game.