title: Tooltip background color in d3 is only filling half
body: <p>I am trying to apply background color to d3 tooltip but it only fills top half square of tooltip area as shown in image below:</p>
  
  <p><a href="https://i.stack.imgur.com/4knO1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4knO1.png" alt="enter image description here"></a> </p>
  
  <p>Here is my code for it:</p>
  
  <pre><code>var tooltip = d3.select("body").append("div")
      .attr("class", "tooltip")
      .style("opacity", 0)
      .style("background",'#BCC5F7');
  </code></pre>
  
  <p>Tooltip example from <a href="http://www.d3noob.org/2013/01/adding-tooltips-to-d3js-graph.html" rel="nofollow noreferrer">http://www.d3noob.org/2013/01/adding-tooltips-to-d3js-graph.html</a></p>