.signup-form {
  background: linear-gradient(135deg, #fffdf7, #f8f4e6);
  border: 2px solid #d4af37; /* ゴールド枠 */
  border-radius: 16px;
  padding: 24px;
  max-width: 500px;
  margin: 20px auto;
  box-shadow: 0 4px 12px rgba(212, 175, 55, 0.4);
  font-family: "Yu Gothic", "Hiragino Kaku Gothic ProN", sans-serif;
  color: #3b3b3b;
}

/* タイトル */
.signup-form__title {
  text-align: center;
  font-size: 20px;
  font-weight: bold;
  color: #b8860b;
  margin-bottom: 20px;
  letter-spacing: 1px;
  border-bottom: 1px solid #d4af37;
  padding-bottom: 8px;
}

/* ラベル */
.signup-form__label {
  display: block;
  font-size: 14px;
  margin-bottom: 6px;
  margin-top: 16px;
  color: #6a5338;
}

/* 入力欄 */
.signup-form__input {
  width: 100%;
  padding: 10px;
  border: 1px solid #d4af37;
  border-radius: 8px;
  font-size: 14px;
  box-sizing: border-box;
  background-color: #fffdf9;
  transition: border 0.3s, box-shadow 0.3s;
}

.signup-form__input:focus {
  border-color: #c6a14d;
  box-shadow: 0 0 6px rgba(198, 161, 77, 0.6);
  outline: none;
}

/* ボタン */
.signup-form__button {
  display: block;
  width: 100%;
  margin-top: 20px;
  padding: 12px;
  font-size: 16px;
  font-weight: bold;
  background: linear-gradient(135deg, #d4af37, #c6a14d);
  color: #fff;
  border: none;
  border-radius: 12px;
  cursor: pointer;
  transition: background 0.3s, transform 0.2s;
  box-shadow: 0 3px 8px rgba(212, 175, 55, 0.5);
}

.signup-form__button:hover {
  background: linear-gradient(135deg, #c6a14d, #a67c00);
  transform: translateY(-2px);
}

.signup-form__button:active {
  transform: translateY(1px);
}

/* メッセージ表示 */
.signup-form__message {
  margin-top: 15px;
  font-size: 14px;
  text-align: center;
  color: #3b3b3b;
}