koel/resources/assets/sass/vendor/_nprogress.scss

/**
 * A stripped-down style of NProgress.
 * Heck, rstacruz (the author) even said:
 * > The included CSS file is pretty minimal... in fact, feel free to scrap it and make your own!
 */
#nprogress {
  /* Make clicks pass-through */
  pointer-events: none;

  .bar {
    background: $colorOrange;

    position: fixed;
    z-index: 1031;
    top: 0;
    left: 0;

    width: 100%;
    height: 2px;
  }

  /* Fancy blur effect */
  .peg {
    display: block;
    position: absolute;
    right: 0px;
    width: 100px;
    height: 100%;
    box-shadow: 0 0 10px $colorOrange, 0 0 5px $colorOrange;
    opacity: 1.0;

    transform: rotate(3deg) translate(0px, -4px);
  }
}

.nprogress-custom-parent {
  overflow: hidden;
  position: relative;

  #nprogress .spinner, #nprogress .bar {
    position: absolute;
  }
}