Squares in a square

n same n in both panels

Everything runs in your browser: the closed-form constructions (grid, Göbel strips and squares with L-extensions) are O(n) and instant for n up to a few million, drawing uses WebGL2 instancing (one draw call), and “Refine” runs the penalty-energy compaction (L-BFGS + basin hopping) in a Web Worker on the CPU for n up to a few hundred. Every displayed packing is checked by an exact separating-axis verifier; “best known” values are the literature records (Friedman / Ellsworth) for n ≤ 324. Scroll to zoom, drag to pan, double-click to fit.