Add tooltip to D3 Icicle visual (Observable)

I am working with this icicle visual on D3 Observable. I need to add a tooltip, so that it works faster and looks better than native browser version.

I tried this:

  var tooltip = d3.select("body")
    .append("div")
    .style("opacity", 0)
    .attr("class", "tooltip")
    .style("background-color", "white")
    .style("border", "solid")
    .style("border-width", "1px")
    .style("border-radius", "5px")
    .style("padding", "10px");

    var mouseover = function(d) {
    tooltip
      .style("opacity", 1)
    };

  var mousemove = function(d) {
    tooltip
      .html("hello")
      .style("left", (d3.mouse(this)[0]+90) + "px")
      .style("top", (d3.mouse(this)[1]) + "px")
  };

  var mouseleave = function(d) {
    tooltip
      .transition()
      .duration(200)
      .style("opacity", 0)
  };

And adding the events onto the rect:

.on("mouseover", mouseover)
.on("mousemove", mousemove )
.on("mouseleave", mouseleave)

Nothing shows up at all when you hover over the rects of the visual. Can elements be appended to the body in D3 observable?

Copyright Notice：Content Author:「Cybernetic」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/59205214/add-tooltip-to-d3-icicle-visual-observable