Luna Lee
Backend software engineer (ex-Amazon Health, One Medical) and actuarial mathematician (UCLA). I build small, honest tools and write about money with real numbers.
Writing
First 90 Days
A money guide for teens about to live independently — first paycheck, first apartment, and the credit-card minimum-payment trap, each walked through with real numbers. Free to read.
Read the first three posts →Tools
FM Toolkit — Exam FM Calculators
Interest theory and loan amortization calculators, verified against known-answer tests. The Interest Theory Calculator is free; the bundle lives on Gumroad.
See the calculators →Code
fm-formalization
Interest-theory mathematics formalized in Lean 4 with Mathlib — accumulation and discount factors and the geometric series behind the annuity formulas, proved with no sorry.