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

.welcome-page{
  min-height: 100dvh;
  display: grid;
  place-items: center;
  background: #ff3f1d;
  color: #fff;
}

.welcome-center{
  text-align: center;
  padding: 24px;
}

.welcome-title{
  font-size: 100px;
  margin: 0 0 8px;
  font-weight: 800;
}

.welcome-sub{
  font-size: 30px;
  margin: 30px;
  opacity: .85;
}

/* ===== スマホ対応 ===== */
@media (max-width: 600px) {
  .welcome-title {
    font-size: 40px;   /* 100px → 半分くらい */
  }

  .welcome-sub {
    font-size: 15px;   /* 30px → 小さめ */
  }
}