Build a Stock Heatmap with Massive and Claude Opus 5.5
In this post, you build a cap-weighted heatmap of every US large cap, about 730 stocks, without writing the code yourself. You describe the app to Claude Opus 5.5 in Claude Code, four prompts in all, and it writes the backend, the universe builder, and the browser app. Massive's full market snapshot returns the latest price for every US ticker in a single request, and that one call is enough to drive a live market heatmap. What a Market Cap Heatmap Shows Say the S&P 500 closes up 0
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