<p>Pure CSS background pattern. Can you figure out how it was made before checking the code? Can you reduce the number of gradients? Let me know!</p>

$d: 8em;
$o: .25*$d;
$c: #160c28;

html {
	background: 
		repeating-conic-gradient(transparent 0% 25%, $c 0% 50%) , 
		radial-gradient(closest-side, 
				transparent calc(100% - 1px), $c), 
		linear-gradient(135deg, #d1dfd6 50%, #efab48 0) $o $o;
	background-size: $d $d, .5*$d .5*$d
}