style.css

/* these css variables hold the main colors so we dont have to retype them everywhere */
:root {
  --page-bg: #0e0f18;
  --frame-bg: #171a26;
  --frame-border: #f3c94a;
}

/* box-sizing border-box means padding wont mess up the width math */
* {
  box-sizing: border-box;
}

/* this sets the page background and makes it fill the whole screen */
html,
body {
  width: 100%;
  min-height: 100%;
  margin: 0;
  /* the radial gradient gives a soft glow at the top of the page */
  background: radial-gradient(circle at 50% 10%, #28324a 0, var(--page-bg) 62%);
  color: #f4f1e8;
  /* monospace font fits the pixel game look */
  font-family: Monaco, Consolas, "Courier New", monospace;
}

/* display grid plus place-items center is the easiest way to center stuff */
body {
  display: grid;
  place-items: center;
  /* overflow hidden stops scroll bars from showing up on the sides */
  overflow: hidden;
}

/* game-shell is the gold bordered frame that wraps around the canvas */
/* it keeps the 16 by 9 aspect ratio no matter the window size */
#game-shell {
  width: min(100vw, calc(100vh * 16 / 9), 1280px);
  aspect-ratio: 16 / 9;
  display: grid;
  place-items: center;
  padding: clamp(6px, 1.2vw, 14px);
  background: var(--frame-bg);
  /* the yellow border and the inset blue glow make it look like an aracde cabnet */
  border: 4px solid var(--frame-border);
  box-shadow: 0 18px 40px rgba(0, 0, 0, 0.45), inset 0 0 0 4px #2e5fd6;
}

/* the important flag forces the canvas to stretch to the shell size */
#game-root,
#game-root canvas {
  width: 100% !important;
  height: 100% !important;
}

/* pixelated rendering keeps the art sharp and not blury when scaled up */
#game-root canvas {
  display: block;
  image-rendering: pixelated;
  /* crisp-edges is the firefox version of the same thing */
  image-rendering: crisp-edges;
}