Student app: Portfolio backtester to test ideas with evidence

Dia, an 11th grader, built Fresh Start Finance to help people examine investment ideas before acting on them. Her portfolio backtester lets users see how a group of assets would have performed over a chosen historical period, compare the results with the S&P 500, and review the numbers in plain language.

Dia’s app was selected as a Judges’ Pick at Demo Day.

The problem

Investment ideas can spread quickly through Reddit, TikTok, and other social channels. For newer investors, it can be hard to tell whether a portfolio recommendation has evidence behind it. Some people follow the advice without checking; others feel uncertain and put off learning about investing altogether.

Dia wanted to give people a way to explore those ideas using historical data. Fresh Start Finance is aimed especially at Gen Z and young millennials, including high school and college students who are learning about personal finance.

The build

Users can enter assets individually or import a CSV, choose a date range, set an initial investment, and run a backtest. Fresh Start Finance then displays performance metrics, a chart comparing the portfolio with the S&P 500, results for individual assets, and a plain-language summary. Hovering over the metrics reveals explanations for users who are new to the terminology.

The app also lets users sign in with Google, save portfolios, and switch between them. Dia demonstrated an install option that lets people use it like an app on their device. A “viral hype validator” is designed to help users examine portfolios they encounter online.

Building the app meant working through data API connections, integrating a database for saved portfolios, and keeping track of changes in GitHub. Dia uses Alpha Vantage for stock data, with Yahoo Finance as a backup when the requested date range needs more information.

Why this matters

Fresh Start Finance turns a broad question—“How would this investment idea have performed?”—into something users can investigate. Rather than relying on a social media claim alone, they can enter a portfolio, choose a historical period, and see how it performed against a familiar benchmark.

The judges recognized Dia’s work as a Judges’ Pick. In explaining the choice, judge Krishna praised “the completeness of the app in terms of technical details and the experience and analytical details put together.” During the Q&A, he added: “This app is complete like in a way you could really use it today right now.”

The judges also offered ideas for what might come next. One suggested exploring how finance influencers’ past portfolio recommendations performed. Another asked about the app’s data sources and update frequency, and suggested adding context about events that may have moved a stock price. Dia has also identified possible next steps of her own, including comparing two portfolios or adding other benchmarks.

Backtesting describes how a portfolio performed in the past; it does not predict future returns. Fresh Start Finance gives learners a way to explore historical performance and build familiarity with investment concepts.

Try it yourself

Fresh Start Finance, built by Dia, is available through its marketplace listing: https://www.flintolabs.com/marketplace/fresh-start-finance-portfolio-backtester. Visit the listing to explore the app and its features.

What would help you feel more confident when evaluating an investment idea you see online? Share your thoughts in the comments.