:root {
  --colour_black: #000000;
  --colour_blue: #0000ff;
  --colour-grey: #808080;
  --colour_yellow: #ffff99;
  --colour_white: #ffffff;
}

html, body {
  padding: 0;
  margin: 0;

  font-size: 10px;
  font-family: Monaco, monospace;
}

*, *::after, *::before {
  box-sizing: border-box;
}