Claude Fable × Semilattice · 12 June 2026

An empty folder at 10:23.
A shipped, validated product by the afternoon.

The story of Debt Freedom Planner — a free UK debt payoff calculator where every product, design, and marketing decision was made with simulated-audience data. Four studies · 804 simulated UK adults · 15 evidence-backed decisions.

The brief

Ship a personal finance product for UK consumers. Win 100 users.

No concept given. No spec. One tool that changes everything: Semilattice — simulated UK audiences accurate enough (90% benchmarked) to do discovery, concept testing, copy testing, and usability research in minutes instead of weeks.

4
Semilattice studies, each feeding the next
804
simulated UK adults (Consumer Finance audience)
~4 min
per study, concept to data

Study 1 · Discovery — "what hurts most?" · view study ↗

Budgeting hurts 5× more than anything else…

"Which personal finance task frustrates you most?"
Budgeting & tracking money46.6%
Paying off debts efficiently10.0%
Tax6.6%
Savings goals3.3%
Pensions2.4%

Study 1 · Discovery — "why do current apps fail?" · view study ↗

…and people don’t want another dashboard. They want to be told what to do.

Biggest frustration with money apps people have tried
"No useful advice — just data"39.7%
Require linking my bank15.8%
Too much manual data entry14.1%
Don't trust them with my info8.3%
→ Decisions D1–D3: give specific actions, never just charts · no bank connection (93.8% prefer it) · data never leaves the device (85.5% abandon over data sharing).

Study 2 · Concept head-to-head · view study ↗

Three concepts entered. One dominated both metrics.

"Which would you try first?" — and who would definitely recommend it after use
Debt Freedom Planner45.8% · 67.6%
Money MOT (score /100)32.9% · 17.6%
Money Snapshot (budget)21.3% · 27.8%
→ Decision D5: build the Debt Freedom Planner. D6: 84.3% share useful tools with friends — one-tap sharing becomes a core feature, not a footer link.

Study 3 · Headline test (5 options) · view study ↗

“Stop guessing.” beat every other headline — 2:1.

Forced choice: "which would make you click?"
"Stop guessing. See exactly when…"46.7%
"What's your debt-free date?"21.3%
"See your date in 60 seconds"13.0%
"The fastest way out of debt"10.5%
"Clear your debts months sooner"7.1%
→ Bonus save: 62.7% found the "60 seconds" claim unbelievable, and speed mattered to just 0.1%. Every speed claim was deleted before launch.

The build — same afternoon

Every validated decision, shipped.

Calculation engine written test-first (11 passing tests) · winning headline verbatim · calm trust strip with "Why is this free?" · instant debt-free date, depth below · one-tap share · StepChange / National Debtline / MoneyHelper signposting. Static page, no server, no tracking.

semilattice-research.github.io/debt-freedom-planner →

Full page screenshot of Debt Freedom Planner

Study 4 · Simulated usability test on the live URL · view study ↗

5 of 5 completed the flow. All five said they’d share it.

100%
task completion — debt-free date, savings, monthly payments, strategy choice
<2 min
every session (97–114 seconds)
3
minor issues found → fixed and re-shipped the same day (v1.1)

"The overdraft warning felt like the tool was actually looking out for me." — the never-clears interest warning was the standout trust moment, cited by 4 of 5 users.

The method, made visible

Four studies. Fifteen decisions. No decision without a number.

Every decision cites the exact data point that produced it, every study inherits the decisions before it, and superseded choices are struck through — never deleted. The whole lineage is an interactive graph.

S1→S4
each study consumed the last one's decisions as fixed context
D1–D15
decision register, each with its evidence pointer
v1.1
two shipped builds, both downstream of the data

Explore the interactive decision graph →

Next · the road to 100 users

The data already wrote the launch plan.

52.4% decide whether to try a money tool based on trusting the source, and 84.3% pass useful tools to friends. So: no ads — launch posts drafted for the UK's trusted money communities (Reddit personal-finance subs, the MoneySavingExpert forum, Show HN), and the share loop is built into the results screen.

52.4%
decide on source trust → trusted communities, not ads
84.3%
would send the link to a friend → sharing is the growth engine
100
users = success, measured by GitHub Pages traffic (no tracking on-site, by design)

github.com/semilattice-research/debt-freedom-planner →