angelosalatino/mortgage-calculator ? reverse-engineered prompt

Build me a simple mortgage calculator app that helps me see how my repayments change over time and how much of each payment goes to interest versus paying down the loan.

I want to enter the mortgage amount, interest rate, term, and payment details, then see a clear breakdown by month and year, plus the total interest paid and how much equity I build. It should also let me compare normal payments with one off extra payments and recurring extra payments, so I can see how much time and money I could save by paying it off faster.

Please make it easy to use and easy to understand, with clean charts and a simple summary of the results. If it helps, look up current docs online while you build it.