body {
  background: #000;
  margin: 0;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-family: sans-serif;
}

#opening-container {
  background: rgba(255, 255, 255, .08);
  padding: 32px 28px;
  border-radius: 16px;
  box-shadow: 0 0 30px rgba(255, 255, 255, .12);
  text-align: center;
  width: min(92vw, 480px);
  display: flex;          /* 縦方向に並べる */
  flex-direction: column;
  align-items: center;
}

h1 {
  margin-top: 0;
  font-size: 2.2rem;
  color: #ff6a00;
  text-shadow: 0 2px 8px rgba(0,0,0,.8);
}

form {
  display: grid;
  gap: 14px;
  width: 100%;
}

label {
  font-size: 1rem;
  opacity: .9;
}

input {
  padding: 12px;
  border-radius: 10px;
  border: 1px solid #ff6a00;
  background: #1e1e1e;
  color: #fff;
  font-size: 1rem;
}

.buttons {
  display: flex;
  gap: 10px;
  justify-content: center;
  margin-top: 6px;
}

button {
  padding: 10px 16px;
  border: none;
  border-radius: 999px;
  background: #ff6a00;
  color: #fff;
  cursor: pointer;
  font-size: 1rem;
}

button.secondary {
  background: #444;
}

button:hover {
  filter: brightness(1.05);
}

/* イントロ文章用 */
#game-intro {
  margin-top: 20px;       /* フォームとの間隔 */
  text-align: left;
  width: 100%;
  max-width: 400px;
  background: #fff8dc;
  color: #000;
  border-radius: 12px;
  padding: 12px;
  box-shadow: 0 0 8px rgba(0,0,0,0.3);
}
#game-intro p {
  margin: 8px 0;
}