What a loan really costs, worked out forty-nine ways. The heart of it is the Icelandic verðtryggt lán — indexed payments, equal-principal, verðbætur month by month, CPI paths, Fisher decomposition, inflation shocks, prepayments and equity build-up, using the bank convention of a monthly real rate with compounded indexation, reproducing a published 30-million-króna schedule to within a rounding krónu.
Around it sit general annuity mathematics, mortgages and housing with PITI, DTI, PMI, closing costs, rent-versus-buy, ARMs and points, consumer credit from car loans and leases to credit-card minimums and debt-avalanche plans, and saving against opportunity cost. Every mode opens from a setup screen with search, categories and favourites, and every one gives amortisation tables, dual-axis charts, cost composition, named input presets and CSV or JSON export.
Twenty-two themes on a white default with a dark toggle, custom colours for all ten tokens and the chart series, seven layout arrangements, eight fonts, adjustable density, radius, panel width and number format, and five languages. Behind the calculators, a bank of 2,122 worked problems in four sets and four full lectures with formulas, worked examples and review questions.