Five fruit circles initially render as apples via an ordinal color scale and size scale, then update through d3 transitions when the data changes—removing a fruit, converting one to a lemon, and filtering another. Hovering a circle triggers `mouseover` and `mouseout` events that call `setSelectedFruit`, toggling a black stroke on the selected fruit. The visualization uses D3 v5's data joins, `selection.enter`, `merge`, `exit`, and `transition` APIs to animate the SVG elements.