Fading an Element from Left to Right

Tell us what’s happening:
Im lost on this one, where did i go wrong fellow coders?

Your code so far


  #ball {
    width: 70px;
    height: 70px;
    margin: 50px auto;
    position: fixed;
    left: 20%;
    border-radius: 50%;
    background: linear-gradient(
    animation-name: fade;
    animation-duration: 3s;

  @keyframes fade {
    50% {
      left: 60%;
      opacity: 0.1px;


<div id="ball"></div>

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0.

Link to the challenge:

Opacity needs a measureless (?!? don’t know the english term - a number without the unit of measurement) number, get rid of that ‘px’ and it would works :slight_smile:

1 Like

Just though you would like to know the term you want is “unitless” :slight_smile: