BAII Fincal
A BA II Plus style financial calculator simulator built for CFA, FRM, CPA and actuarial candidates — with step-by-step built-in tutorials for TVM, NPV, IRR, bond pricing, depreciation and break-even.
Independent apps · iOS & macOS
Small tools, made to last.
diosapp is a one-person studio building focused apps: a financial calculator for serious exam candidates, two unhurried puzzles, and a Mac reader that turns Markdown into something you can actually send. No ads, no accounts, no noise — just software that earns its place.
The catalog
Four apps. Four very different jobs.
Each one started with a specific problem worth solving — and stayed small enough to solve it properly. A fifth, FoldPress for the Mac, is on the way.
Linked Lines
The classic Color Lines puzzle, refined: line up five same-colored balls on a 9×9 board, clear them, and chase your high score against friends on Game Center. Color-blind friendly, dark mode included.
SudokuPlus
Classic Sudoku with five difficulty levels, a fresh daily challenge, and full offline play. One small purchase, zero ads, zero account — just a clean grid whenever you want a minute to yourself.
Emma's Revenge
A couture story block puzzle: place the pieces, clear full rows and columns, and follow Emma through ten acts and one hundred handmade stages as she wins back the manor that was taken from her.
Coming soon
FoldPress
A Mac reader for people who write in Markdown and have to hand the result to someone else: read it at speed, check the tables and code blocks, then export a clean PDF, PNG or self-contained HTML in one keystroke.
Latest
What's new
Emma's Revenge is live on the App Store
A couture story block puzzle: 100 handmade stages across ten acts, unlimited undo, no timer, no accounts. Free on iPhone and iPad.
SudokuPlus is live on the App Store
Five difficulty levels, daily challenge, full offline play. A quiet, ad-free Sudoku for iOS 17 and later.
BAII Fincal updated with new tutorials
Step-by-step walkthroughs for bond pricing, depreciation and break-even — built right into the calculator.
Linked Lines adds dark mode & color-blind palette
Light and dark themes with a redrawn ball set, plus a color-blind friendly palette.
Ready when you are
Pick one, and see where small software gets you.
Every app is free to try or a small one-time purchase. No subscriptions, no tracking, no dark patterns.