$c0: #e8122e;
$c1: #161125;
$d: 8em;

html {
	background: 
		conic-gradient($c1 0 0), 
		radial-gradient($c0 50%, #000 calc(50% + 1px)) 
			50%/ #{$d} #{$d}, 
		linear-gradient(90deg, $c0 50%, #000 0) 
			50%/ #{$d};
	background-blend-mode: lighten, difference
}