html { 
  --_g: #036564 35%, #0000 36%;
  background: 
	  radial-gradient(at 100% 100%, var(--_g)),
	  radial-gradient(at 0    0   , var(--_g))
    #E8DDCB;
  background-size: 4em 4em;
  /* 35% = 100%/(2*sqrt(2)) */
}