body {
  height: 2000px;
  margin: 0;
  font-family: Arial, sans-serif;
  background-color: #121212;
  color: white;
}

#scrollToTopBtn {
  position: fixed;
  bottom: 60px;
  right: 50px;
  z-index: 9999;
  width: 50px;
  height: 50px;
  background-color: transparent;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 0 10px #00f2fe, 0 0 20px #4facfe;
  transition: opacity 0.4s ease, visibility 0.4s ease, transform 0.3s ease;
  animation: glow 2s infinite alternate;
  overflow: hidden;
}

#scrollToTopBtn.show {
  opacity: 1;
  visibility: visible;
}

#scrollToTopBtn img,
#scrollToTopBtn span {
  position: absolute;
  width: 24px;
  height: 24px;
  transition: opacity 0.4s ease;
}

#scrollToTopBtn img {
  opacity: 0;
  animation: none;
}

#scrollToTopBtn span {
  color: white;
  font-size: 24px;
  opacity: 0;
}

#scrollToTopBtn.logo-visible img {
  opacity: 1;
  animation: bounceIn 0.6s ease;
}

#scrollToTopBtn.arrow-visible img {
  opacity: 0;
}

#scrollToTopBtn.arrow-visible span {
  opacity: 1;
}

@keyframes glow {
  0% {
    box-shadow: 0 0 10px #00f2fe, 0 0 20px #4facfe;
  }
  100% {
    box-shadow: 0 0 20px #00f2fe, 0 0 30px #4facfe;
  }
}

@keyframes bounceIn {
  0% {
    transform: scale(0.5) translateY(30px);
    opacity: 0;
  }
  50% {
    transform: scale(1.6) translateY(-20px);
    opacity: 1;
  }
  70% {
    transform: scale(1.1) translateY(8px);
  }
  100% {
    transform: scale(1) translateY(0);
    opacity: 1;
  }
}

#scrollToTopBtn:hover {
  transform: scale(1.1);
}

/* Mobile Responsive */
@media (max-width: 600px) {
  #scrollToTopBtn {
    width: 45px;
    height: 45px;
    bottom: 45px;
    right: 30px;
  }

  #scrollToTopBtn img,
  #scrollToTopBtn span {
    width: 18px;
    height: 18px;
    font-size: 18px;
  }
}