The amazing Financial Time Machine!
The Travelers!

Financial Time Machine — Our Story

Inspiration

In Loki, the TVA monitors a single "Sacred Timeline" and prunes any branches that deviate. We thought — what if those branches weren't threats, but financial opportunities? What if you could stand at any point in your past, make a different money decision, and watch the ripple hit your present net worth?

That's the Financial Time Machine. Your bank history is the Sacred Timeline. Every "what if" creates a branch. The TVA would prune them — we explore them.

How We Built It

MongoDB Atlas stores real bank transactions — the Prime Timeline
Gemini 2.5 Flash acts as our "Temporal Architect," generating structured what-if scenarios from natural language
Custom SVG rendering plots branching timelines with clickable nodes, Bézier curves, zoom/pan — no chart library
Plaid Link (sandbox) connects bank accounts through the official flow
All API routes run inside Vite middleware — one npm run dev runs everything

The math is straightforward: saving \$200/month for 10 years gives you \$24,000. Investing it at 10% annual return gives you ~\$41,310 — a 72% difference, visualized as two diverging branches.

What We Learned

Prompt engineering is half the product — getting Gemini to return consistent structured JSON took many iterations. Custom SVG beats chart libraries when you need full interactivity. And the Loki metaphor works — people instantly understand "branching timelines" for financial decisions.

Challenges

We migrated from yearly to monthly granularity mid-build — a full rewrite in one sitting. And branch-from-branch recursion required careful parent-balance inheritance to get right.