What is a-share-heatmap?

This is an open-source tool for visualizing the Chinese A-share stock market as an interactive heatmap. The A-share market refers to shares listed on the Shanghai and Shenzhen stock exchanges in China, and this project compresses thousands of individual stocks into a single treemap visualization where you can instantly see which sectors and stocks are rising or falling. Each colored rectangle represents a single stock. The size of the rectangle reflects the stock's market weight, bigger blocks belong to companies with higher market value. The color depth shows how much the stock has risen or fallen on a given day, letting you scan the entire market in seconds rather than scrolling through numbers. You can switch between different market scopes, the full Shanghai-Shenzhen market, CSI 300, CSI A500, the ChiNext board, or the STAR Market, and adjust the time period to today, last 5 days, last 20 days, or year-to-date. The chart is interactive: zoom in, drag to pan, hover to see individual stock details, and double-click to jump to an external data source. A one-click screenshot feature and a market overview panel showing rising, flat, and falling stock counts are also included. It is built with Next.js App Router, React, Canvas 2D, Tailwind CSS, and Vercel Serverless Functions, and can be deployed to Vercel with one click. Data is cached server-side to reduce API pressure on page refreshes. Useful for individual investors wanting a quick market overview, financial platforms needing an embeddable market summary widget, or developers learning large-scale treemap rendering with Canvas.