html{
  box-sizing: border-box;
}
*{
  box-sizing: inherit;
}

.wrapper{
  max-width: 1000px;
  margin: 40px auto;
  text-align: center;
  position: relative;
}
.btn{
  display: block;
  margin: 0 auto;
  width: 200px;
  border: 2px solid darkcyan;
  padding: 10px 30px;
  color: darkcyan;
  text-transform: uppercase;
  font-family: arial;
  cursor: pointer;
  transition: .3s all;
}

.btn:hover{
  background-color: darkcyan;
  color: white;
}

.popup{
  
  alignment: center;
  width: 200px;
  background-color: darkcyan;
  padding: 30px;
  text-transform: uppercase;
  font-family: arial;
  color: white;
  font-size: 18px;
  position: absolute;
  left: 50%;
  text-align: center;
  transform: translate(-50%);
  top: -999px;
  transition: .5s all linear;
}

.popup input{
  width: 100%;
  border: 0;
  margin: 10px 0;
  height: 35px;
  padding: 5px;
  outline: none;
}

.submit{
  background-color: #fff;
  cursor: pointer;
}

#callback{
  display: none;
}

#callback:checked ~ .popup{
  top: 200px;
}

.close{
  display: block;
  position: absolute;
  transform: rotate(45deg);
  font-size: 24px;
  top: 5px;
  right: 10px;
  cursor: pointer;
}