NB heatmap

<p>The heatmap can be drawn directly by clicking the mouse.</p><p>What is drawn is a png image with a transparent background.</p><p><br></p><p>website: <a href="https://www.nbcharts.com/heatmap/index.php" rel="noreferrer noopener nofollow ugc" target="_blank">https://www.nbcharts.com/heatmap/index.php</a></p><p>video: <a href="https://www.youtube.com/watch?v=NnBtNbcaxuU" rel="noreferrer noopener nofollow ugc" target="_blank">https://www.youtube.com/watch?v=NnBtNbcaxuU</a></p>