.mensetsu {
  text-align: center;
  height: 500px;
  /* line-height: 50px; */
  /* font-size: 20px; */
  font-weight: bold;
}

#theme,
#Contents,
#question,
#sub {
  font-size: 120%;
  margin: 1rem;
  height: 35px;
}

#number {
  margin: 5px;
  padding: 10px;
}

.btn--submit,
input.btn--submit {
  font-size: 1.6rem;
  color: #fff;
  background-color: #0099ff;
  padding: 1rem 3rem;
}

.btn--submit:hover,
input.btn--submit:hover {
  color: #fff;
  background: #3333ff;
}

input.btn--radius {
  border-radius: 100vh;
}

.theme,
.sub {
  opacity: 0;
  animation-name: feedIn;
  animation-duration: 1s;
  animation-fill-mode: forwards;
  /*これで値を保持*/
}

.question {
  opacity: 0;
  animation-name: feedIn;
  animation-duration: 1s;
  animation-fill-mode: forwards;
  animation-delay: 200ms;
}

.Contents {
  opacity: 0;
  animation-name: feedIn;
  animation-duration: 1s;
  animation-fill-mode: forwards;
  animation-delay: 600ms;
}

/* CSSアニメーションの設定 */
@keyframes feedIn {
  0% {
    opacity: 0;
    /*初期状態では透明に*/
  }

  100% {
    opacity: 1;
  }
}