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Inspiration I kept buying things and regretting it like a week later. I'd look at my savings and just feel bad. I tried looking for apps that could help me but everything either needed my bank account, cost money, or was clearly made for adults. Nothing was made for someone my age. So I just built one. What it does You type in what you want to buy and it tells you if you should. Green means go for it, yellow means think carefully, red means not right now. But it doesn't just say yes or no. It shows you how much of your savings you'd be spending, how long it takes to earn that back, and what that money would actually be worth in 10 years if you invested it instead. You can also tell it if you're paying with cash, debit, or credit and it factors that in too. There's also a goals tracker, a bills calculator, a spending history, an AI advisor, live market charts, a product comparison tool, and a learn section with lessons on stuff like taxes, investing, and credit cards that most of us were never taught in school. How I built it It's one HTML file. No framework, no build step. I used Supabase for accounts and syncing data, Groq with Llama 3.3 70B for the AI advisor, Chart.js for the charts, and the Wikipedia and Open Food Facts APIs for the comparison feature. It's on GitHub Pages and works as a PWA so you can install it on your phone. Challenges I ran into Getting the verdict right was hard. The first version just looked at your total savings vs the price which wasn't that useful. I had to rebuild it to actually factor in your bills, your income, and the opportunity cost so the answer meant something real. Mobile was also harder than I expected. I didn't use any framework so every single layout thing had to be done by hand. It took a while but I learned a lot from it. Accomplishments that I'm proud of 27 real users signed up in the first month with zero advertising, just from Google finding it. The app is fully deployed, works on any phone, and doesn't require linking a bank account. Getting it indexed by Google as a solo 8th grade developer with no team and no budget felt like a real milestone. What I learned Shipping something real is way different from just building something. Once actual people signed up I started seeing bugs and situations I never thought about. The 27 users who found it just from Google in the first month showed me that more than anything else. What's next for Think To Buy A browser extension so you can get a verdict without leaving whatever site you're shopping on. Better personalization in the AI advisor based on your spending history. And getting it in front of more students who never learned this stuff in school.
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