Drop CSV files (two columns: x, y). Raw spectrum first, then one or more basis spectra. Linear mode solves y ≈ Σ cᵢ · bᵢ(x) by least squares. Nonlinear mode fits parametric peaks (Gaussian / Lorentzian / pseudo‑Voigt) and optional baseline.
1) Raw Spectrum
2) Basis Spectra (1…∞)
Toggle which bases to include in the fit.
3) Options
Use a tiny λ (e.g., 1e-8 to 1e-4) if the system is ill‑conditioned; enable positivity to enforce NNLS.