*{
  margin: 0;
  padding: 0;
  color: inherit;
  text-decoration: none;
  font-style: normal;
  font-family: inherit;
  font-size: inherit;
  list-style: none;
  box-sizing: border-box;
  border-collapse: collapse;
  outline: inherit;
}

:root{
  --deep-blue:#204680;
  --blue:#2b96b4;
  --light-blue:#78B7D0;
  --yellow:#FFDC7F;
}

html{
  width: 100%;
  height: 100%;
  height: -webkit-fill-available;
  font-size: 10px;
}

body{
  min-height: 100vh;
  color: #000;
  line-height: 1.8;
  font-family: "Noto Sans JP", sans-serif;
  background: #fff; 
  display: flex;
  flex-direction: column;
}

.flex{
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
}

/* ----------header---------- */
header{
  padding: 40px 0;
  background: var(--deep-blue);
  color: #fff;
}

.header_inner{
  text-align: center;
}

.header_inner h1{
  font-size: 3rem;
  font-weight: 600;
  letter-spacing: .2rem;
}

/* ----------usage-page---------- */
.usage-page {
  width: 100%;
  background: url(../images/AdobeStock_924675142_Preview.png) center/cover;
  padding: 30px 0;
  margin: auto;
  flex: 1;
}

.form {
  width: 720px;
  background: #fff;
  margin: 0 auto 30px;
  text-align: center;
  box-shadow: 0 0 20px 0 rgba(0, 0, 0, 0.2), 0 5px 5px 0 rgba(0, 0, 0, 0.24);
  z-index: 10;
}

.form .explanation{
  padding: 15px 0;
  background: var(--yellow);
  font-size: 1.6rem;
}

.form .usage-form{
  padding: 30px;
}

.contents {
  margin-top: 20px;
  justify-content: center;
}

.contents li{
  width: 40%;
  margin: 10px;
}

.contents a {
  background: #dceffd;
  padding: 15px;
  font-size: 1.4rem;
  font-weight: 400;
  -webkit-transition: all 0.3 ease;
  transition: all 0.3 ease;
  display: block;
}

.contents a:hover {
  background: #c1e4fc;
}

.form .message {
  margin: 10px 0;
  font-size: 1.4rem;
}

.form .message a {
  color: var(--blue);
  font-weight: 500;
}

.form .message1 {
  font-size: 1.6rem;
  font-weight: 600;
}

.form .message1 a {
  font-weight: 600;
}

/* ----------footer---------- */
footer{
  width: 100%;
  background: var(--deep-blue);
  color: #fff;
  font-size: 1rem;
  text-align: center;
  padding: 20px 0;
  flex-shrink: 0;
}

@media screen and (max-width: 768px) {
  /* ----------header---------- */
  header{
    padding: 20px 0;
  }

  /* ----------usage-page---------- */
  .form {
    width: 420px;
  }

  .form .explanation{
    padding: 15px;
  }

  .form .usage-form{
    padding: 20px;
  }

  .contents {
    margin-top: 10px;
    justify-content: center;
  }
  
  .contents li{
    width: 40%;
    margin: 10px;
  }
  
  .contents a {
    height: 80px;
  }

  .contents a>span {
    display: inline-block;
  }
}

@media screen and (max-width: 500px) {
  /* ----------header---------- */
  header{
    padding: 15px 0;
  }

  .header_inner h1{
    font-size: 2rem;
  }

  /* ----------usage-page---------- */
  .usage-page {
    padding: 20px;
  }

  .form {
    width: 300px;
  }

  .form .explanation{
    padding: 10px;
    font-size: 1.4rem;
  }

  .form .usage-form{
    padding: 15px;
  }

  .form .message1 {
    font-size: 1.4rem;
  }

  .contents li{
    width: 44%;
    margin: 8px;
  }

  .contents a {
    height: 65px;
    padding: 8px;
    font-size: 1.3rem;
  }

  /* ----------footer---------- */
  footer{
    padding: 15px 0;
    font-size: .8rem;
  }
}