body {
  background-position: center;
  background-size: cover;
  background-repeat: no-repeat;
}

#cover {
  width: 35%;
  position: absolute;
  z-index: -1;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

#cover img {
  width: 100%;
  -webkit-filter: drop-shadow(5px 5px 15px #00ff2f);
  filter: drop-shadow(5px 5px 15px #00ff2f);
}

.tipBtn {
  position: absolute;
  top: 85%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 32px;
  filter: drop-shadow(5px 5px 5px #ffeb3b);
  color: #fff;
  animation: likes 3s infinite;
  text-decoration: none;
}

.tipBtn:hover {
  cursor: pointer;
}

@keyframes likes {
  0% {
    opacity: 1;
  }
  5% {
    opacity: 0.95;
  }
  10% {
    opacity: 0.9;
  }
  15% {
    opacity: 0.85;
  }
  20% {
    opacity: 0.8;
  }
  25% {
    opacity: 0.75;
  }
  30% {
    opacity: 0.7;
  }
  35% {
    opacity: 0.65;
  }
  40% {
    opacity: 0.6;
  }
  45% {
    opacity: 0.55;
  }
  50% {
    opacity: 0.5;
  }
  55% {
    opacity: 0.55;
  }
  60% {
    opacity: 0.6;
  }
  65% {
    opacity: 0.65;
  }
  70% {
    opacity: 0.7;
  }
  75% {
    opacity: 0.75;
  }
  80% {
    opacity: 0.8;
  }
  85% {
    opacity: 0.85;
  }
  90% {
    opacity: 0.9;
  }
  95% {
    opacity: 0.95;
  }
  100% {
    opacity: 1;
  }
}

footer {
  position: fixed;
  bottom: 10px;
}

footer a {
  text-decoration: none;
  color: #000;
}

@media screen and (max-width: 768px) {
  #cover {
    width: 80%;
  }
  .tipBtn {
    top: 80%;
  }
}