Reading the heatmap
Each tile is one stock listed on US; switch between all stocks, Top 500 stocks or the 500 most traded. Bigger tiles traded more value (price × volume) in the last session, so the largest names show the money flow. Green tiles are up and red tiles are down; the deeper the colour, the bigger the move. Switch the colour to 1 week, 1 month or 3 months to see trends instead of today's move.