html, body {
  height: 100%;            /* make sure both fill the viewport */
  margin: 0;               /* remove default margins */
  padding: 0;
}

body::before {
  content: "";
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5); /* black overlay with 50% opacity */
  z-index: -1; /* keeps overlay behind the content */
}

body {
  background-image: url('images/PS.jpg'); /* path to your image */
  background-size: cover;       /* makes it fill the screen */
  background-position: center;  /* centers the image */
  background-repeat: no-repeat; /* don’t tile it */
  color: white;                 /* sets the font color for all text */
  font-family: Arial, sans-serif; /* optional: change font */
}

header {
  background-color: #0055ff;
  color: white;
  padding: 10px;
  text-align: center;
}

nav a {
  color: white;
  text-decoration: none;
  margin: 0 10px;
}

main {
  padding: 20px;
}