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It's a good educational game but I think the square and rectangle are mixed up. In the beginning, it showed me what I thought was a square, but the right solution was rectangle, so I assumed I had misjudged the sides. Near the end of the game, it clearly showed a rectangle with two sides being much longer than the others, but the solution was square.
Did you try using the Hint button? The square and the rectangle are definitely tough to tell apart, and the square's left and right sides seem longer than the top and bottom sides, but give it another try and use the hint button to see what I'm talking about. Thanks for commenting :D