Generate or upload a correlation matrix. Click any off-diagonal cell to see its feasible range given the other entries, then drag along the axis or type a value into the cell to vary it and watch the other entries' ranges shift in response.
The bar beneath each cell marks that entry's feasible range.
λ_min is the smallest eigenvalue; the matrix stays valid while it is ≥ 0. Drag past the zero crossing and the matrix turns red.