Changing the font

In the source/stylesheets/screen.css.scss file, import your fonts after the general stuff comment:

@import url("https://fonts.googleapis.com/css?family=Roboto");html {
  font-family: sans-serif;
  -ms-text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%
}

Then, change the %default-font part in the source/stylesheets/_variables.scss file to include your font first:

%default-font {
  font-family: Roboto, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
  font-size: 14px;
}