body { font-family: 'Noto Sans JP', 'Yu Gothic', sans-serif; margin: 0; background: #f9f9f9; color: #222; }
header { background: #005bac; color: #fff; padding: 0.2em 0 0 0; text-align: center; }
header h1, header p {
  margin: 0;
  padding: 0.1em 0;
}
.nav-toggle {
  display: none;
  background: #005bac;
  color: #fff;
  border-radius: 2px;
  font-size: 1em;
  text-align: left;
  padding: 0.2em;
  margin: 0em;
  width:100%;
  cursor: pointer;
  z-index: 1001;
}
nav {
  background: #eee;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  transition: max-height 0.3s;
}
nav a {
  margin: 0.5em 1em;
  color: #005bac;
  text-decoration: none;
  font-weight: bold;
}
nav a:hover {
  text-decoration: underline;
}
main {
  max-width: 900px;
  margin: 2em auto;
  padding: 1em;
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 2px 8px #ddd;
}
footer {
  background: #eee;
  color: #555;
  text-align: center;
  padding: 1em;
  margin-top: 2em;
}
footer p {
  margin: 0;
}
@media (max-width: 600px) {
  .nav-toggle {
    display: block;
  }
  nav {
    flex-direction: column;
    max-height: 0;
    overflow: hidden;
    position: static;
    background: #eee;
    z-index: 1000;
    box-shadow: 0 2px 8px #bbb;
  }
  nav.show {
    max-height: 500px;
    padding-bottom: 1em;
  }
  main {
    margin: 1em; padding: 0.5em;
  }
}
.correct {
  color: red;
  font-weight: bold;
  display: none;
}