body { background: black; position: fixed; overflow: hidden;width: 100%; height: 100%;}
.outer {
  text-align: center;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translateX(-50%) translateY(-50%);
}
.container, .slides {
  position: relative;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 10px;
  top: 0;
}
.slides {
  position: absolute;
}
.box, .slide {
  border-radius: 5px;
  background-color: white;
  position: relative;
  width: 100px;
  height: 100px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: Ubuntu;
  font-weight: bold;
  color: white;
  font-size: 35px;
}
.slide {
  background-color: rgb(255,220,0);
}
.transit {
  transition: all 0.1s;
}
.backButton {
  background: white;
  color: black;
  border-radius: 5px; 
  margin-top: 10px;
  height: 50px;
  row-span: 4;
  font-family: Ubuntu;
  font-size: 25px;
  display: flex;
  justify-content: center;
  align-items: center;
  transition: all 0.2s;
  cursor: pointer;
  color: black;
}
.backButton:hover {
  color: white;
  background-color: rgb(255,220,0);
}