natural number game use fira code by glatavento

/* ==UserStyle==
@name         natural number game use fira code
@version      20211008.01.56
@namespace    userstyles.world/user/glatavento
@description  Force [natural number game](https://www.ma.imperial.ac.uk/~buzzard/xena/natural_number_game/) to use Fira Code font.
@author       glatavento
@license      No License
==/UserStyle== */

@-moz-document url-prefix("https://www.ma.imperial.ac.uk/~buzzard/xena/natural_number_game/") {
.monaco-editor .view-lines {
    font-feature-settings: normal !important;
    font-variant-ligatures: contextual !important;
    font-family: "Fira Code" !important;
}
}