body, html {
  margin: 0;
  padding: 0;
  height: 100%;
  font-family: 'Poppins', sans-serif;
  background: linear-gradient(to right, #f0f8ff, #e0f7fa);
  overflow: hidden;
}

#particles-js {
  position: fixed;
  width: 100%;
  height: 100%;
  z-index: -1;
}

.card-container {
  perspective: 1200px;
  width: 350px;
  height: 480px;
  margin: auto;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.card {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.8s ease;
}

.card.girar {
  transform: rotateY(180deg);
}

.side {
  position: absolute;
  width: 100%;
  height: 100%;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(10px);
  border-radius: 20px;
  box-shadow: 0 0 20px rgba(0, 140, 255, 0.2);
  padding: 40px 30px;
  color: #003366;
  text-align: center;
}

.front {
  backface-visibility: hidden;
}

.back {
  transform: rotateY(180deg);
  backface-visibility: hidden;
}

h2 {
  margin-bottom: 30px;
  font-size: 28px;
  color: #0055cc;
}

.user-box {
  position: relative;
  margin-bottom: 25px;
}

.user-box input {
  width: 100%;
  padding: 10px 0;
  background: transparent;
  border: none;
  border-bottom: 2px solid #0055cc;
  color: #003366;
  font-size: 16px;
  outline: none;
}

.user-box label {
  position: absolute;
  top: 0;
  left: 0;
  color: #666;
  pointer-events: none;
  transition: 0.5s;
  padding: 10px 0;
}

.user-box input:focus ~ label,
.user-box input:valid ~ label {
  top: -20px;
  color: #ff6600;
  font-size: 12px;
}

.glow-button {
  background: none;
  border: 2px solid #ff6600;
  padding: 10px 20px;
  color: #ff6600;
  font-size: 16px;
  border-radius: 10px;
  cursor: pointer;
  transition: 0.4s;
}

.glow-button:hover {
  background: #ff6600;
  color: white;
  box-shadow: 0 0 15px #ff6600, 0 0 30px #ff6600;
}

.mensaje {
  margin-top: 10px;
  font-size: 14px;
  color: #cc0000;
}

.flip-text {
  margin-top: 20px;
  font-size: 14px;
  color: #666;
}
.flip-text a {
  color: #0055cc;
  text-decoration: none;
}
.flip-text a:hover {
  text-decoration: underline;
}