Played two rounds of the daily sizes. Matching the desk lamp against the banana felt great, and the instant "error 5.8%" breakdown with the real number is a very satisfying payoff. The way the scale bar changes as you drag (10 cm, then 1 m, then 2 m) teaches you a lot too. Two suggestions: the surfboard silhouette includes waves and a sun, so it was hard to tell which part is the board, and a tighter outline would make fair guesses easier. Also the main slider jumps a lot per pixel, so a finer control near the middle would help. Small thing: the "真实" label still shows in Chinese in English mode. Lovely idea.