title: Positioning tooltip with mouse hover
body: <p>I am using the code found at the following link:</p>
  
  <p><a href="https://www.d3-graph-gallery.com/graph/heatmap_tooltip.html" rel="nofollow noreferrer">https://www.d3-graph-gallery.com/graph/heatmap_tooltip.html</a></p>
  
  <p>If you download this code and then view it in a browser, you will notice the tooltip position on mouseover is no longer relative to the cell in the heat map but rather appears as a long rectangle towards the bottom. I noticed the same after integrating this code with my own. </p>
  
  <p>What do I have to add to force the tooltip to appear in a position relative to the cell of the heat map? Any help would be greatly appreciated. </p>