Thank you so much for your help.
It's working very well now!

img, #cubbies-overlay{ -moz-transition-property: margin, box-shadow, z-index; -moz-transition-duration: 0.1s; -webkit-transition-property: margin, box-shadow, z-index; -webkit-transition-duration: 0.1s; } .cubbies-selected{ z-index: 9999; box-shadow: 3px 3px 8px -1px blue !important; cursor: pointer !important; margin: -3px 3px 3px -3px; } .cubbies-selected:active{ box-shadow: 2px 2px 5px -1px darkblue !important; margin: -1px 1px 1px -1px; } #cubbies-overlay{ position: fixed; z-index: 9999; bottom: 30px; left: 30px; box-shadow: 0 2px 3px rgba(0,0,0,0.8); border: none; } #cubbies-overlay:hover{ box-shadow: 0 2px 3px rgb(0,0,0); }