body {
    background-color: #FFFF00;
    color: #763D14;
    padding: 2em;
    font-family: "Handjet", sans-serif;
    font-size: 1.5em;
}

a {
   color: #800000; 
} 

img {
    border: 2em outset  #66d3fa;
    border-radius:2em;
}

h1 {
  font-family: "Silkscreen", sans-serif;
  font-size: 3em;
  text-align: center;
}

.container {
  display: flex;
  align-items: flex start;
  justify-content: center;
  flex-wrap: wrap;
}

.box {
  /* PLAY WITH THE FLEX-BASIS TO SET THE SIZE OF THE BOXES - DON'T GO OVER 45% */
  flex-basis: 20%;
  margin: .1em;
  border: 6.7px solid black;
  border-radius: 1px;
  padding: 6.7em;
}

/* SETTING THE IMAGE WIDTH HERE INSTEAD OF IN HTML. REMOVE WIDTH="XXX%" FROM THE HTML IMAGE TAGS */
.box img {
  max-width: 100%;
  display: block;
  margin: auto;
}
/* SIDE TO SIDE */
/* Create the animation... */
@keyframes side {
   from {
      margin-left: 0%;
      transform: translateY(0px);
   }
   to {
      margin-left: 70%;
      transform: translateY(-20px);
      /* 70% works because the image width is set to 30% - update your percent according to your element's width */
   }
}

/* ...and then apply it: */
.sidetoside {
   animation-duration: 3s;
   animation-name: side;
   animation-iteration-count: infinite;
   animation-direction: alternate;
   animation-timing-function: linear;
   display: inline-block;

      
   }