Build/Build & digital tools
Make a calculator for a decision you repeat
Define explicit inputs and arithmetic, then create an inspectable interactive comparison.
Here’s what it could look like.
An illustrative example to show the direction. Your details will make it different.
Calculate the total for a craft meetup. Fixed room cost $120. Materials $8 per attendee. 18 attendees. No other costs in this example. Total = fixed cost + attendees × materials cost. Per-person share = total / attendees; zero attendees has no per-person result.
FORMULA Total = 120 + 18 × 8 = $264. Per-person share = 264 / 18 = $14.666…; display $14.67 as a rounded estimate. INTERFACE Inputs: attendees, fixed cost, materials per attendee. Outputs: total and per-person estimate, with the formula visible. EDGE CASES 0 attendees: show fixed total $120 and per-person share 'not applicable'. Negative attendees: validation error. Blank material cost: ask for a value; do not silently assume zero. ROUNDING NOTE 18 payments of $14.67 total $264.06. If collecting exact shares, handle the six-cent difference explicitly rather than claiming the rounded shares sum exactly.
A good way to get there.
- 01
Write the arithmetic independently of the interface and identify units.
- 02
Create worked examples, including zero, boundary, and invalid values.
- 03
Generate a compact calculator that shows its formula and assumptions.
- 04
Verify the output against the worked examples before relying on the tool.
The prompt behind this idea
Replace the bracketed details or make it yours using the form.
Specify and prototype a calculator for [Add decision]. Inputs: [Add inputs]. Rules: [Add rules]. Known examples: [Add examples]. Keep calculations deterministic and visible. Validate missing, negative, nonnumeric, and out-of-range inputs. Show units and rounding rules. Separate unknown real-world costs from arithmetic. Do not add hidden assumptions or invented data. Give the formula, example results, acceptance checks, and a concise interface/build brief.
Give it a second look.
- Arithmetic passes supplied examples.
- Rounding does not silently change totals.
- Units and unknown costs are visible.
“Add an exact collection plan that distributes any rounding remainder across attendees and proves that the payments sum to the total.”
This fictional calculator excludes taxes, fees, and other real-world costs unless the user supplies them.
The capability to look for
A coding assistant or artifact environment; the result still needs to run and be checked.
Find a tool for the jobHow these ideas and prompts are made