InkCalc: Notepad calculator for Mac & iPhone with on-device AI

Hi Product Hunt! I'm Kentaro, a solo developer in Tokyo, and InkCalc is my notepad calculator for Mac, iPhone and iPad. The idea: the formula is the note. Instead of a lone number, you keep lines like rent = 1450 and each = total / 2 that still make sense when you read them back a month later. What it does: • Percentages the way people say them: 1000 - 20% - 10% = 720 • 40+ units and live currency conversion, inline • Dates: today + 90 days, or a fixed date like 2026-10-06 + 14 days • AI: plain words → formula, fix a broken line, summarize a note. On-device with Apple Intelligence, or bring your own Claude/OpenAI key • Japanese IME full-width input works too Pricing: $1.99/month with a 1-month free trial. I'd love your feedback, especially on what you'd want to calculate in a note like this.