body{
  font-family: system-ui, -apple-system, Segoe UI, Roboto, "Noto Sans JP", sans-serif;
  margin:0;
  background-color:#e8f4ff;
}

/* ===== Header ===== */
header{
  padding:18px;
  border-bottom:2px solid #7aaed6;
  background-color:#d6ecff;
  display:flex;
  justify-content:space-between;
  align-items:center;
}

h1{
  margin:0;
  font-size:22px;
  color:#174d7a;
}

/* ===== Lang Button ===== */
.lang-switch{
  font-size:20px;
  color:#174d7a;
  text-align:right;
}

/* ===== Home Button ===== */
.home-btn{
  text-decoration:none;
  background:#ffffff;
  color:#174d7a;
  padding:8px 14px;
  border-radius:10px;
  border:2px solid #7aaed6;
  font-weight:600;
  font-size:14px;
  transition:all .2s ease;
}

.home-btn:hover{
  background:#f4faff;
  border-color:#3c7fb1;
}

.lesson-note{
  text-align:center;
  font-size:18px;
  margin:10px 0px 0px 0px;
  color:#555;
}

/* スマホ */
@media (max-width: 768px) {
  header{
    padding:5px 10px 8px 10px;
  }

  h1{
    font-size:110%;
  }

  /* ===== Lang Button ===== */
  .lang-switch{
    font-size:80%;
  }

  /* ===== Home Button ===== */
  .home-btn{
    font-size:80%;
  }
  
  .lesson-note{
    font-size:90%;
  }
}



/* ===== Main ===== */
main{
  max-width:900px;
  margin:0 auto;
  padding:28px 16px;
}

ul{
  list-style:none;
  padding:0;
  margin:0;
}

li{
  margin-bottom:18px;
}

/* ===== Card Link ===== */
.card-link{
  display:block;
  background:#ffffff;
  border:2px solid #7aaed6;
  border-radius:16px;
  padding:18px;
  text-decoration:none;
  transition:all .2s ease;
  box-shadow:0 2px 6px rgba(0,0,0,0.05);
}

.card-link:hover{
  background:#f4faff;
  border-color:#3c7fb1;
  transform:translateY(-2px);
  box-shadow:0 4px 12px rgba(0,0,0,0.08);
}

/* ===== Title ===== */
.title{
  font-weight:700;
  font-size:18px;
  color:#174d7a;
}

/* ===== Meta ===== */
.meta{
  font-size:13px;
  color:#4a6f8c;
  margin-top:8px;
}