more elaborate code example #123
                
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I found the code example not very explanatory.
Also the input of
(Left, right, bottom, top)is counter intuitive to me and should be on some list for when a new GUI framework is created. It should be at least(Left, right, top, bottom), I would prefer a canvas that's just defined with(x_length, y_length). That doesn't explicitly forbid using negative values. But that's probably going to break stuff.