nav {
  margin: 5px auto 0;
  position: relative;
  max-width: 1250px;
  height: 40px;
  padding: 5px;
  background-color: #fff;
  border: 0px solid #ddd;
  border-radius: 5px;
  display: flex;
  align-items: center;
  text-align: center;
  justify-content: center;
  font-size: 0;
  box-sizing: border-box; /* 追加 */
}

nav a {
  box-sizing: border-box; /* パディングを幅に含める */
  padding: 5px;
  line-height: 50px;
  height: 40px;
  font-size: 15px;
  display: inline-block;
  position: relative;
  z-index: 1;
  text-decoration: none;
  text-transform: uppercase;
  text-align: center;
  border-radius: 10px;
  color: #778899;
  cursor: pointer;
  /* 5個にそろえて20%ずつ */
  width: 20%;
}

/* アニメーション部分 */
nav .animation {
  position: absolute;
  height: 100%;
  top: 0;
  z-index: 0;
  transition: all 0.5s ease 0s;
  border-radius: 5px;
}

/* 5つに対応したアニメーション指定 */
nav .start-1,
nav a:nth-child(1):hover ~ .animation {
  width: 20%;
  left: 0;
  background-color: #ffc0cb;
}
nav .start-2,
nav a:nth-child(2):hover ~ .animation {
  width: 20%;
  left: 20%;
  background-color: #c3e8ff;
}
nav .start-3,
nav a:nth-child(3):hover ~ .animation {
  width: 20%;
  left: 40%;
  background-color: #eee8aa;
}
nav .start-4,
nav a:nth-child(4):hover ~ .animation {
  width: 20%;
  left: 60%;
  background-color: #c3ebc3;
}
nav .start-5,
nav a:nth-child(5):hover ~ .animation {
  width: 20%;
  left: 80%;
  background-color: #f7e9fd;
}

.footer {
  background-color: #ffffff;
  opacity: 0.85;
  position: fixed;
  bottom: 0vh;
  width: 100%;
}

.footer_navbar {
  background-color: #ffffff;
  padding: 0px;
  display: flex;
  align-items: center;
  bottom: 0;
  width: 100%;
  position: fixed;
  justify-content: space-between;
  z-index: 1000; /* フッターを前面に表示 */
}