html, body {
  margin: 0;
  height: 100%;
}

body {
  background: url("/images/bg.jpg") no-repeat center center;
  background-size: cover;
  font-family: sans-serif;
}

/* ボタン配置 */
.overlay {
  position: absolute;
  bottom: 15%;
  width: 100%;
  text-align: center;
}

/* 共通ボタン */
.btn {
  display: inline-block;
  margin: 0 10px; /* ← gap の代替 */
  text-decoration: none;
  padding: 14px 40px;
  font-size: 18px;
  border: 1px solid #ffffff;
  color: #ffffff;

  /* fallback → rgba */
  background: rgb(0, 0, 0);
  background: rgba(0, 0, 0, 0.4);
}

/* FANZA */
.btn.fanza {
  border-color: #ff4f4f;
}

/* ヤフオク */
.btn.yahoo {
  border-color: #ffcc00;
  color: #ffcc00;
}

/* 年齢確認 */
#age-check {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.85);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
}

.age-box {
  background: #000;
  border: 1px solid #fff;
  padding: 30px;
  text-align: center;
  max-width: 320px;
  color: #fff;
}

.age-box p {
  margin-bottom: 15px;
  font-size: 14px;
}

.age-box button {
  margin: 10px;
  padding: 10px 20px;
  font-size: 14px;
  cursor: pointer;
}