/* Fullscreen animated 7-color gradient background */
body {
  margin: 0;
  font-family: "Segoe UI", sans-serif;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: linear-gradient(
    135deg,
    #f7f751,
    #fcd34d,
    #ff9f59,
    #ff6cb4,
    #e44eee,
    #7f5af0,
    #00c2ff
  );
  background-size: 1000% 1000%;
  animation: gradientShift 25s ease infinite;
}

/* Gradient animation */
@keyframes gradientShift {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

/* Center Card with glass and glowing border */
.container {
  padding: 2rem 3rem;
  border-radius: 16px;
  text-align: center;
  max-width: 400px;
  backdrop-filter: blur(10px);
  background: rgba(255, 255, 255, 0.15);
  border: 2px solid rgba(255, 255, 255, 0.3);
  box-shadow: 0 0 20px rgba(255, 255, 255, 0.2);
  transition: background 0.3s ease, border 0.3s ease;
  color: #fff;
}

/* Title */
.container h1 {
  font-size: 1.8rem;
  margin-bottom: 0.5rem;
  color: #ffffff;
  text-shadow: 0 0 5px #000;
}

/* Subtext */
.container p {
  font-size: 1rem;
  color: #e0e0e0;
}

/* Button Style */
button {
  margin-top: 1rem;
  padding: 12px 24px;
  background-color: rgba(255, 255, 255, 0.85);
  color: #111;
  font-size: 1rem;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.3s ease, transform 0.2s ease;
}

button:hover {
  background-color: #ffffff;
  transform: scale(1.05);
}

/* BMI Result Text */
#result {
  margin-top: 1rem;
  font-weight: bold;
  color: #fff;
}