header {
  text-align: center;

}

header img {
  max-width: 100%;

}

header p {
  font-size: 18px;
  margin-top: 10px;
}

main {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin-top: 20px;
}

.banner-container {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-around;
}

.banner-container .banner {
  flex: 1 1 45%;
  margin: 10px;
}
/* ??????????? */
@media (max-width: 750px) {
  .banner-container .banner {
    flex-basis: 100%; /* ?????????????? */
    margin: 5px 0; /* ??????????? */
  }
}
.tutorial {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
}
.banner {
  margin-top: 20px;
  text-align: center;
}

.banner a {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-decoration: none;
  color: black;
  font-size: 14px;
}

.banner img {
  max-width: 100%;
}

.banner p {
  margin-top: 10px;
}

.bannerlogo {
  margin-top: 30px;
  text-align: center;
}
.bannerlogo img {
  max-width: 50%;
}
/* .ad-container {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
  }

  .ad {
    flex: 1;
    margin: 0 10px;
  } */
/*.ad {
  margin-top: 20px;
  font-size: 14px;
  text-align: right;
}*/
.update {
  margin-top: 20px;
  font-size: 14px;
  text-align: right;
}

.language-switcher {
  position: absolute;
  top: 10px;
  right: 10px;
}

.language-switcher a {
  color: #999999; /* ????? */
  text-decoration: none;
  font-size: 18px;
}

.language-switcher a:hover {
  color: #cccccc; /* ?????????? */
}