Here is some simple CSS code snippets that I have found useful.

Disable over scroll effect

html {
  overscroll-behavior: none
}

https://developer.mozilla.org/en-US/docs/Web/CSS/overscroll-behavior

Radial gradient to cover all of the background

html {
  width: 100vw;
  min-height: 100vh;
  background: radial-gradient(#676767, #232323);
}

Overlay that blurs and dims background

.overlay {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  width: 100%;
  background-color: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(5px);
  z-index: 7;
}