*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  width: 100%;
  height: 100%;
}

body {
  background-color: #0a0a0a;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}

.container {
  display: flex;
  align-items: center;
  justify-content: center;
}

.emoji {
  font-size: 28.125vw;
  line-height: 1;
  user-select: none;
  cursor: pointer;
}

@keyframes heartbeat {
  0%   { transform: scale(1); }
  14%  { transform: scale(1.2); }
  28%  { transform: scale(1); }
  42%  { transform: scale(1.2); }
  70%  { transform: scale(1); }
  100% { transform: scale(1); }
}

.emoji.beating {
  animation: heartbeat 0.9s ease-in-out infinite;
}