I built a free UK personal finance app as a single HTML file. Here's why, and how.

I'm not a developer. A few months ago I couldn't write a line of code. I'm a British backpacker living in Australia, and about the only thing I knew about software was that I'd been frustrated by it for years. Here's the thing — I'm a self-diagnosed personal finance geek. Spend a day with me and I guarantee I'll bring it up more times than you'd like. And yet every tool I tried to manage my money either wanted my bank login, a monthly subscription, or was built entirely around American tax law with a thin coat of paint slapped over it for UK users. So I'd been limping along with spreadsheets. They did the job, I guess. But they never scratched the itch. I could never work out an efficient system to log my spending, so it turned into a two hour job at the end of every month. And they were completely useless for anything forward-looking — working out my CGT position, modelling what happens if I overpay my mortgage, figuring out when I could realistically stop working. Then AI got loud en