Two tile shapes (square + rhombus, 45°) tile the plane quasiperiodically via substitution rules with inflation ratio 1+√2 (silver ratio).
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The Ammann–Beenker tiling has 8-fold symmetry and is generated by substitution: each square → 1 square + 4 half-rhombi; each rhombus → 2 rhombi + 1 half-square.
Inflation ratio = 1+√2 ≈ 2.414 (silver ratio δ_S). Diffraction pattern shows sharp Bragg peaks arranged with 8-fold symmetry — a quasicrystal!