How to read the heatmap
A heatmap shows the whole market in one picture. If most tiles are green, most large coins are up; if a few tiles are bright red while the rest are grey, those coins are moving on their own news.
The colour scale tops out at 8% for the 24 hour view and 15% for the 7 day view. Anything beyond that gets the strongest colour. Hover over or tap a tile to see the coin's price, or open it for the full coin page.