styles.css

:root {
  --guiScaleFactor: 3;
  --guiScale: 3;
  --chatWidth: 320px;
  --chatHeight: 180px;
  --chatScale: 1;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  height: 100vh;
  overflow: hidden;
}

.dirt-bg {
  position: absolute;
  top: 0;
  left: 0;
  background: url('textures/1.17.1/gui/options_background.png'), rgba(0, 0, 0, 0.7);
  background-size: 16px;
  background-repeat: repeat;
  width: 100%;
  height: 100%;
  transform-origin: top left;
  transform: scale(2);
  background-blend-mode: overlay;
}

@font-face {
    font-family: minecraft;
    src: url(minecraftia.woff);
}

@font-face {
    font-family: mojangles;
    src: url(mojangles.ttf);
}

body {
  overflow: hidden;
  position: relative;
  margin:0;
  padding:0;
  height: 100vh;
  font-family: sans-serif;
  background: #333;
  /* background: linear-gradient(#141e30, #243b55); */
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

canvas {
  position: absolute;
  top: 0;
  left: 0;
	height: 100%;
	width: 100%;
	font-size: 0;
	margin: 0;
	padding: 0;
}

#ui-root {
  position: absolute;
  top: 0;
  left: 0;
  transform-origin: top left;
  transform: scale(var(--guiScale));
  width: calc(100% / var(--guiScale));
  height: calc(100% / var(--guiScale));
  z-index: 10;
  image-rendering: optimizeSpeed;
  image-rendering: -moz-crisp-edges;
  image-rendering: -webkit-optimize-contrast;
  image-rendering: -o-crisp-edges;
  image-rendering: pixelated;
  -ms-interpolation-mode: nearest-neighbor;
  font-family: minecraft, mojangles, monospace;
}

@media only screen and (max-width: 971px) {
  #ui-root {
    transform: scale(2);
    width: calc(100% / 2);
    height: calc(100% / 2);
  }
}

@media only screen and (max-height: 670px) {
  #ui-root {
    transform: scale(2);
    width: calc(100% / 2);
    height: calc(100% / 2);
  }
}

@media only screen and (max-width: 561px) {
  #ui-root {
    transform: scale(1);
    width: calc(100% / 1);
    height: calc(100% / 1);
  }
}

@media only screen and (max-height: 430px) {
  #ui-root {
    transform: scale(1);
    width: calc(100% / 1);
    height: calc(100% / 1);
  }
}