body, html {
  margin: 0;
  height: 100%;
  background: linear-gradient(135deg, #20477a 0%, #92e6ff 70%, #092c5c 100%);
  font-family: sans-serif;
  min-height: 100vh;
  background-attachment: fixed;
  background-size: 200% 200%;
  animation: cartoon-gradient-move 32s ease-in-out infinite;
}

/* Animated background gradient movement */
@keyframes cartoon-gradient-move {
  0% { background-position: 0% 60%; }
  50% { background-position: 100% 40%; }
  100% { background-position: 0% 60%; }
}

.cartoon-bg-bubble {
  position: fixed;
  border-radius: 50%;
  opacity: 0.7;
  z-index: -1;
  animation-timing-function: ease-in-out;
  will-change: transform, opacity;
  filter: blur(1px);
}
.bubble1 {
  width: 140px; height: 140px; background: #ffcc00;
  bottom: -150px; left: 10%; animation: floatUp 17s infinite;
}
.bubble2 {
  width: 100px; height: 100px; background: #49b0ef;
  bottom: -110px; left: 20%; animation: floatUp 15s infinite 2s;
}
.bubble3 {
  width: 90px; height: 90px; background: #ffcc00;
  bottom: -80px; left: 30%; animation: floatUp 19s infinite 6s;
}
.bubble4 {
  width: 125px; height: 125px; background: #fff;
  bottom: -130px; left: 40%; opacity: 0.45; animation: floatUp 16s infinite 3s;
}
.bubble5 {
  width: 120px; height: 120px; background: #092c5c;
  bottom: -170px; left: 55%; animation: floatUp 21s infinite 7s;
}
.bubble6 {
  width: 185px; height: 185px; background: #ffcc00;
  bottom: -180px; left: 72%; opacity: 0.29; animation: floatUp 29s infinite 15s;
}
.bubble7 {
  width: 70px; height: 70px; background: #49b0ef;
  bottom: -90px; left: 82%; animation: floatUp 23s infinite 9s;
}

/* Animation for all bubbles */
@keyframes floatUp {
  0% { transform: translateY(0) scale(1); opacity: 0.6; }
  45% { opacity: 1; }
  100% { transform: translateY(-150vh) scale(0.92); opacity: 0; }
}

/* Twinkling stars little effect */
.cartoon-bg-star {
  position: fixed;
  z-index: -1;
  pointer-events: none;
  animation: star-twinkle 2.8s infinite ease-in-out;
  opacity: 0.6;
}
.star1 { left: 18vw; top: 7vh; font-size: 1.5rem; animation-delay: 0.5s; }
.star2 { left: 45vw; top: 17vh; font-size: 1.8rem; animation-delay: 1.3s; }
.star3 { left: 79vw; top: 12vh; font-size: 1.25rem; animation-delay: 2.1s; }
.star4 { left: 60vw; top: 15vh; font-size: 1.1rem; animation-delay: 2.8s; }
.star5 { left: 31vw; top: 2vh; font-size: 1.6rem; animation-delay: 1s; }

@keyframes star-twinkle {
  0%, 100% { opacity: 0.45; }
  50% { opacity: 1; }
}

@media (max-width: 700px) {
  .cartoon-bg-bubble { filter: blur(3px); }
  .cartoon-bg-star { font-size: 1rem !important; }
}

/* prefers-reduced-motion for accessibility */
@media (prefers-reduced-motion: reduce) {
  .cartoon-bg-bubble, .cartoon-bg-star {
    animation: none !important;
  }
  body, html { animation: none !important; }
}


#backToTopBtn {
  position: fixed;
  bottom: 40px;
  right: 40px;
  background: linear-gradient(135deg, #092c5c 75%, #ffd966 100%);
  color: #fff;
  border: none;
  border-radius: 50%;
  width: 54px;
  height: 54px;
  font-size: 2.2rem;
  box-shadow: 0 8px 28px rgba(9,44,92,0.16);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.42s, box-shadow 0.3s, background 0.3s;
  z-index: 99;
  display: flex;
  align-items: center;
  justify-content: center;
  outline: none;
}

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

#backToTopBtn:hover,
#backToTopBtn:focus {
  background: linear-gradient(135deg, #ffd966 85%, #092c5c 100%);
  color: #092c5c;
  box-shadow: 0 12px 34px #ffcc0040;
}

.backtotop-arrow {
  display: inline-block;
  font-size: 2.1rem;
  font-weight: bold;
  transition: transform 0.32s cubic-bezier(.4,1.8,.65,1.25);
}

#backToTopBtn:hover .backtotop-arrow {
  transform: translateY(-6px) scale(1.13);
}

/* Responsive */
@media (max-width:600px) {
  #backToTopBtn {
    bottom: 16px;
    right: 16px;
    width: 38px;
    height: 38px;
    font-size: 1.1rem;
  }
}