body-overlay

.body-overlay{
  position: relative;
  z-index: 99;
  height: 100%;
  transition: opacity 0.5s;
}
.body-overlay::after{
    position: absolute;
    top: 0;
    right: 0;
    width: 0;
    height: 0;
    background: rgba(0, 0, 0, 0.3);
    content: '';
    opacity: 0;
    transition: opacity 1s;
}
.canvas-slid, .canvas-sliding{
    .body-overlay::after {
        width: 100%;
        height: 100%;
        opacity: 1;
        transition: opacity 0.5s;
    }
}