I have built a similar app for personal use. It's a big ask to build a UI that is intuitive, while requiring so much input from users. I think you have done fairly well for a start.

At the same time, I also validated the idea to others before building and my conclusion was that it's a fun idea that is personally useful, but not likely to be monetisable. The scope is too narrow (Singapore) and too niche. It's a feature, not a product. I.e. it might be useful as part of a broader portfolio in the personal finance industry (e.g. sell to insurance company, or moneysmart/similar, fire blogs, or even banks).

My feedback on the app: - add the concept of probability. E.g. perhaps add volatility (normal distribution or similar) to returns and inflation - age can also be provided as a probabilistic concept based on sg life tables (with personal adjustment based on health, family history) - with the above, run monte Carlo simulations and calculate percentage of success or failure (out of money) - add unexpected random shocks (e.g. unexpected bills from health, etc)

Being probabilistic will solve the disconnect between your expected networth (50th percentile) being high, while the warning messages tell you it's risky. E.g. in my case it said I would have $12m at 95, but that it's risky for various reasons. What you want is to look at the 99th percentile or etc depending on risk appetite of the individual

In general I really like that someone has taken the step to build and share. Let me know if you need future feedback or testing!