Why it resists
What makes Eternity II hard at its core: phase transitions, rigidity, entropy, forbidden patterns, all the structural walls every solver eventually hits.
Why it's hard
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Which wall stops which method
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Complex theory: counting the search before you run it
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Tuned to the hardness peak
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Designed to be unsolvable: the recipe
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The rigidity wall
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Why basin-hopping looks impossible
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Where the mismatches live
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Forbidden patterns
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No forced moves
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Where you place the hints beats how many
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Piece theft, where solvers die
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The rare colors live on the frame
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The border balance
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Entropy and the area law