90 degree angles are practical for avoiding wasted space
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*rectangles
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squares compose easily in 2d, and qubes in 3d
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we understand them easily, and their composition easily
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they are one of the simplest shapes we know of
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so the objects don't slide
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stacking works because the plane of the qubes are perpendicular to gravity
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qubes also compose well wrt. gravity: stacking
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because: gravity
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.. everything that stands perpendicular on the earths surface
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90 degree angles actually happen in nature
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e.g. a saw can cut a line, and you just make 4 cuts
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it's easy to create a rectangle
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