Babylon.js/Playground/splitbox.css

x-splitbox {
  position: relative;
  display: -webkit-box;      /* OLD - iOS 6-, Safari 3.1-6 */
  display: -moz-box;         /* OLD - Firefox 19- (buggy but mostly works) */
  display: -ms-flexbox;      /* TWEENER - IE 10 */
  display: -webkit-flex;     /* NEW - Chrome */
  display: flex;             /* NEW, Spec - Opera 12.1, Firefox 20+ */
  height: 100%;
  overflow: hidden;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  -ms-box-sizing: border-box;
  box-sizing: border-box;
  -webkit-box-orient: horizontal;
  -moz-box-orient: horizontal;
  -ms-box-orient: horizontal;
  box-orient: horizontal;
  -webkit-flex-direction: row;
  -moz-flex-direction: row;
  -ms-flex-direction: row;
  flex-direction: row;
}

x-splitbox[direction="column"] {
  -webkit-box-orient: vertical;
  -moz-box-orient: vertical;
  -ms-box-orient: vertical;
  box-orient: vertical;
  -webkit-flex-direction: column;
  -moz-flex-direction: column;
  -ms-flex-direction: column;
  flex-direction: column;
}

x-splitbox > *:not([splitter]) {
  min-width: 0;
  min-height: 0;
  -webkit-box-flex: 1;
  -moz-box-flex: 1;
  -webkit-flex: 1;
  flex: 1;
  -ms-flex: auto;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  -ms-box-sizing: border-box;
  box-sizing: border-box;
}

x-splitbox[dragging], x-splitbox > [splitter] {
  -moz-user-select: -moz-none;
  -khtml-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  user-select: none;
  -webkit-user-drag: none;
}

x-splitbox > [splitter] {
  display: block;
  position: relative;
  min-width: 0px !important;
  max-width: 0px !important;
  cursor: ew-resize;
  background: #fff;
  opacity: 0.6;
}

  x-splitbox > [splitter]:before {
    content: " ";
    display: block;
    position: absolute;
    width: 0.8em;
    height: 100%;
    opacity: 0;
    background: inherit;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    -ms-box-sizing: border-box;
    box-sizing: border-box;
    -webkit-transform: translate(-50%, 0);
    -ms-transform: translate(-50%, 0);
    transform: translate(-50%, 0);
  }

  x-splitbox > [splitter]:after {
    content: url('data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIGhlaWdodD0iMWVtIiB3aWR0aD0iMWVtIiB2aWV3Qm94PSIwIDAgMTAyNCAxMDI0Ij48cGF0aCBmaWxsPSJyZ2JhKDAsMCwwLDAuNzUpIiBkPSJNNzU4IDIzNGwyMzIgMjc4LTIzMiAyNzgtNjYtNTQgMTg2LTIyNC0xODYtMjI0ek00NzAgNTU0di04NGg4NHY4NGgtODR6TTcyNiA0NzB2ODRoLTg2di04NGg4NnpNMjk4IDU1NHYtODRoODZ2ODRoLTg2ek0zMzIgMjg4bC0xODYgMjI0IDE4NiAyMjQtNjYgNTQtMjMyLTI3OCAyMzItMjc4eiI+PC9wYXRoPjwvc3ZnPg==');
    position: absolute;
    top: 50%;
    left: 50%;
    height: 1em;
    padding: 0.05em;
    background: inherit;
    border-radius: 100%;
    -webkit-box-shadow: 0 1px 1px 0px rgba(0,0,0,0.4);
    -ms-box-shadow: 0 1px 1px 0px rgba(0,0,0,0.4);
    box-shadow: 0 1px 1px 0px rgba(0,0,0,0.4);
    -webkit-transform: translate(-50%, -50%);
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
  }

  x-splitbox[direction="column"] > [splitter] {
    cursor: ns-resize;
    min-width: auto !important;
    max-width: none !important;
    min-height: 0px !important;
    max-height: 0px !important;
  }

  x-splitbox[direction="column"] > [splitter]:before {
    width: 100%;
    height: 0.8em;
    -webkit-transform: translate(0%, -50%);
    -ms-transform: translate(0%, -50%);
    transform: translate(0%, -50%);
  }

  x-splitbox[direction="column"] > [splitter]:after {
    -webkit-box-shadow: 1px 0 1px 0px rgba(0,0,0,0.4);
    -ms-box-shadow: 1px 0 1px 0px rgba(0,0,0,0.4);
    box-shadow: 1px 0 1px 0px rgba(0,0,0,0.4);
    -webkit-transform: translate(-50%, -50%) rotate(90deg);
    -ms-transform: translate(-50%, -50%) rotate(90deg);
    transform: translate(-50%, -50%) rotate(90deg);
  }

  x-splitbox > [splitter]:hover, x-splitbox > [splitter][dragging] {
    opacity: 1;
    z-index: 2;
  }

  x-splitbox > [splitter][dragging]:before {
    opacity: 0.3;
  }


@media screen and (max-device-width: 415px) {
  x-splitbox > [splitter]:before {
    display: block;
  }

    x-splitbox[direction="column"] > [splitter] {
      display: block;
    }
}