body {
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='400' height='200'><defs><linearGradient id='concreteBase' x1='0' y1='0' x2='0' y2='1'><stop offset='0%' stop-color='%23bbb'/><stop offset='100%' stop-color='%23999'/></linearGradient><filter id='concreteTexture'><feTurbulence type='fractalNoise' baseFrequency='1.9' numOctaves='5' result='noise'/><feColorMatrix type='saturate' values='0.2'/></filter></defs><rect width='100%' height='100%' fill='url(%23concreteBase)' filter='url(%23concreteTexture)'/></svg>");
  background-size: cover;
  background-repeat: no-repeat;
  background-attachment: fixed;
}