the App Shelf
Tools rather than games — handmade, no ads, no sign-ups. Things worth keeping in a tab. New ones get added as they're built.
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Calculator
A scientific calculator with a hundred keypad layouts — twenty families, from Ivory Classic and Ten-Key to Broadsheet, Orbit and Reverse Polish, each in five variants. Sixty palettes and five languages. Behind the keypad sit six workbenches: algebra that expands, factors and solves exactly, with surds, complex roots, partial fractions, linear systems and number theory; linear algebra with determinants, inverses, RREF, LU and QR, eigenvalues and singular values; calculus with symbolic differentiation, adaptive integration, limits, Taylor series, gradients, curl and Runge-Kutta; physics with eighty relations solvable for any variable; and chemistry with a full periodic table giving every element's charges, mass, configuration, melting and boiling points, density and ionisation energy, plus molar masses and an exact equation balancer. Graphing, unit and base conversion and a constants library round it out, and every result from every workbench lands in a history you can download as JSON and load back in.
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Loan Cost Calculator
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.
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