Somebody wrote : 1-D is simpler than 2-D.
The answer.
The 1-D figure is explained by "theory of string-particle".
The result is written in the book "The trouble with Physics" by Lee Smolin.

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Other wrote: a triangle is simpler than circle.
The answer.
The triangle has angles.
To create angles needs some kind of forces.
Without forces every flat geometrical figure would change into circle.
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