input[id^="spoiler"]{
 display: none;
}
input[id^="spoiler"] + label {
  display: inline-block;
  width: 100%;
  margin: 0 auto;
  padding: 5px 20px;
 
  color: rgb(0, 0, 0);
  text-align: left;
  font-size: 24px;
  border-radius: 8px;
  cursor: pointer;
  transition: all .6s;
}
input[id^="spoiler"]:checked + label {
  color: #333;
  background: #ccc;
}
input[id^="spoiler"] ~ .spoiler {
  width: 90%;
  height: 0;
  overflow: hidden;
  opacity: 0;
  margin: 10px auto 0; 
  padding: 10px; 
  background: #eee;
  border: 1px solid #ccc;
  border-radius: 8px;
  transition: all .6s;
}
input[id^="spoiler"]:checked + label + .spoiler{
  height: auto;
  opacity: 1;
  padding: 10px;
}