Wardian Loan planner
Try it
The app runs here in your browser. Nothing you type leaves it; what it saves stays in this browser, and Claude is off here. Open it on its own.
Download loan-planner.wardian Import it in Wardian: Settings → Import.
A Wardian suite: six sealed apps that plan a loan together. WebAssembly does the amortization.
| App | Slot | Job | Contract |
|---|---|---|---|
inputs | aside | Amount, rate, term, extra payment, start month, currency. Checks and remembers them. | emits loan:changed (retained); storage |
engine | — | Runs engine.wasm: the monthly payment and a row per month. | provides schedule; asset |
planner | — | Turns each change into one plan for every viewer, with and without the extra payment. | listens loan:changed; needs engine.schedule; emits plan:ready (retained) |
summary | main | Monthly payment, total interest, total paid, payoff date, what the extra saves. | listens plan:ready |
chart | main | Balance over time, with and without the extra payment. Hover or use the arrow keys. | listens plan:ready |
export | main | Downloads the schedule as CSV. | listens plan:ready; claude:downloads |
How a change flows: inputs emits loan:changed → planner calls engine.schedule twice
(as asked, and without the extra payment) → planner emits plan:ready → summary,
chart and export each draw their part. The engine runs once per change, not once per viewer.
shared/format.js (money, months, durations) is listed in suite.json "scripts", so every frame
gets its own copy. Apps never share objects.
The engine's source is src/lib.rs: payment, schedule, alloc and dealloc. Rebuild
engine.wasm with ./build.sh. Its buffers are 8-byte aligned so JavaScript can read them as a
Float64Array.
The numbers use the standard formula with no rounding to cents each month, so the totals can differ from a lender's statement by a few cents.
This page is apps/loan-planner/README.md in the repository. Something wrong or missing? Change that file.