body {
  font-family: 'Segoe UI', 'ヒラギノ角ゴ ProN', 'メイリオ', sans-serif;
  margin: 0;
  background: #f5f6fa;
  color: #333;
}

h1, h2, h3 {
  margin-bottom: 10px;
}

#auth-section, #main-section {
  max-width: 420px;
  margin: 30px auto;
  background: #fff;
  padding: 24px;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

form {
  margin-bottom: 20px;
}

label {
  display: block;
  margin-top: 12px;
  margin-bottom: 4px;
}

input, select, button {
  width: 100%;
  padding: 10px;
  margin-top: 4px;
  margin-bottom: 12px;
  border-radius: 6px;
  border: 1px solid #ccc;
  box-sizing: border-box;
  font-size: 1em;
}

button {
  background: #4e8cff;
  color: #fff;
  border: none;
  cursor: pointer;
}

button:disabled {
  background: #aaa;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 14px;
}

nav {
  margin-bottom: 14px;
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

nav button {
  width: auto;
  padding: 6px 16px;
}

#content-area > div {
  margin-top: 10px;
}

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

li {
  background: #f0f4ff;
  margin-bottom: 6px;
  padding: 7px 12px;
  border-radius: 6px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

@media (max-width: 600px) {
  #auth-section, #main-section {
    max-width: 100%;
    padding: 12px;
    border-radius: 0;
  }
  nav {
    flex-direction: column;
    gap: 6px;
  }
}