body {
  text-align: center;
  margin: 0;
  font-family: "Noto Sans JP", sans-serif;
  /* background-color: #a8c6ed; */
  background-image: url(img/tatami.jpg);
}

header {
  position: fixed;
  width: 100%;
  background-color: white;
  /* opacity: 0.7; */
  /*background-color: #ade0d6;*/
}

nav {
  margin: 0 auto;
  display: flex;
  align-items: center;
  flex-direction: column;
}
nav ul {
  display: flex;
  padding: 0;
  margin: 0;
  list-style: none;
}
nav ul li {
  padding: 20px 40px;
  font-size: 20px;
}
a {
  text-decoration: none;
}
a:link {
  color: #24211c;
}
a:visited {
  color: #24211c;
}

main {
  padding-top: 130px;
}

.ABOUT {
  max-width: 1000px;
  margin-left: auto;
  margin-right: auto;
}

mark {
  background: linear-gradient(transparent 50%, #fff3b5 0%);
}
.mark2 {
  background: linear-gradient(transparent 50%, #edd5a8 0%);
  font-size: 24px;
}

.introduction_1 {
  background-color: #f5f5f5;
  border-radius: 20px;
  padding: 140px 100px;
  background-image: url(img/title_text.png), url(img/game_1.png);
  background-size: 55%, 20%;
  background-position: 100px 120px, 700px 35px;
  background-repeat: no-repeat;
  margin-bottom: 60px;
}

.introduction_2 {
  background-color: #f5f5f5;
  border-radius: 20px;
  background-image: url(img/karuta_1.png);
  background-size: 13%;
  background-position: 810px 295px;
  background-repeat: no-repeat;
  margin-bottom: 60px;
  line-height: 30px;
}

.introduction_2 p:first-child {
  padding: 40px 0px;
  font-size: 36px;
  margin: 0;
}

.introduction_2 p:last-child {
  font-size: 20px;
  padding: 40px 0px;
}

.introduction_3 {
  background-color: #f5f5f5;
  border-radius: 20px;
  background-image: url(img/juunihitoe.png);
  background-size: 15%;
  background-position: 815px 350px;
  background-repeat: no-repeat;
  line-height: 35px;
  margin-bottom: 60px;
}

.introduction_3 p:first-child {
  padding: 40px 0px;
  font-size: 36px;
  margin: 0;
}

.introduction_3 p:last-child {
  font-size: 20px;
  color: #e66157;
  padding-bottom: 25px;
}

.HOW {
  max-width: 1000px;
  margin-left: auto;
  margin-right: auto;
  background-color: #f5f5f5;
  border-radius: 20px;
  line-height: 35px;
  margin-bottom: 60px;
}

.HOW p:first-child {
  padding: 40px 0px;
  font-size: 36px;
  margin: 0;
}

.HOW img {
  width: 18%;
}

.bottom_space {
  padding-bottom: 40px;
}

.space {
  margin-top: 80px;
}

@media screen and (max-width: 520px) {
  /* 520px以下に適用されるCSS*/
  nav ul li {
    padding: 20px 20px;
    font-size: 15px;
  }

  main {
    padding: 100px 20px;
  }

  .introduction_1 {
    padding: 70px;
    background-size: 60%, 30%;
    background-position: 15px 65px, 220px 25px;
    margin-bottom: 30px;
  }

  .introduction_2 {
    background-size: 13%;
    background-position: 810px 295px;
    margin-bottom: 30px;
    line-height: 30px;
    text-align: left;
    margin: 0;
  }

  .introduction_2 p {
    margin-left: 15px;
    margin-right: 15px;
  }

  .introduction_2 p:first-child {
    padding-top: 20px;
    padding-bottom: 10px;
    font-size: 18px;
    text-align: center;
  }

  .introduction_2 p:last-child {
    font-size: 15px;
    padding: 15px;
    padding-bottom: 50px;
    margin: 0;
  }

  .introduction_3 {
    margin-top: 30px;
    text-align: left;
  }

  .introduction_3 p {
    margin-left: 15px;
    margin-right: 15px;
  }

  .introduction_3 p:first-child {
    padding-top: 20px;
    padding-bottom: 10px;
    font-size: 20px;
    margin: 0;
    text-align: center;
  }

  .introduction_3 p:last-child {
    font-size: 17px;
    padding-bottom: 25px;
  }

  .HOW {
    border-radius: 20px;
    line-height: 35px;
    margin-bottom: 60px;
  }

  .HOW p:first-child {
    padding-top: 20px;
    padding-bottom: 10px;
    font-size: 18px;
    margin: 0;
    text-align: center;
  }

  .HOW p {
    text-align: left;
    margin-left: 15px;
    margin-right: 15px;
  }

  .mark2 {
    font-size: 16px;
    text-align: center;
  }

  .bottom_space {
    padding-bottom: 40px;
  }

  .space {
    margin-top: 20px;
  }
}