How to display additions?

If number of covered statements increases, need to display +1, +20, ...
Similar to 2048 score additions https://glebbahmutov.com/2048/
See code in 2048/style/main.scss

``` sass
.score-addition {
position: absolute;
right: 30px;
color: red;
font-size: $height;
line-height: $height;
font-weight: bold;
color: rgba($text-color, .9);
z-index: 100;
@include animation(move-up 600ms ease-in);
@include animation-fill-mode(both);
}
```

The issue names no project file or test; start by locating the code that renders covered-statement totals and compare the referenced 2048/style/main.scss animation example. Done means increases show a transient +1, +20, or similar addition beside the score.

Written by the indexing model from the issue text.