* {
  box-sizing: border-box;
  margin: 0;
}
body {
  font-family: sans-serif;
  font-size: 16px;
  color: #333;
  width: 400px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 90vh;
  background: #094760;
}
h1 {
  text-transform: uppercase;
  color: #999;
}
.contagem {
  font-size: 8rem;
  font-weight: bold;
  color: #92c3e4;
}
button {
  color: #fff;
  border: none;
  padding: 10px 20px;
  border-radius: 5px;
  font-size: 18px;
  cursor: pointer;
  margin-top: 20px;
  margin-left: 1rem;
  margin: 1rem 0.5rem;
}
#aumentar {
  background-color: #4caf50;
}
#diminuir {
  background-color: #f44336;
}
#reiniciar {
  background-color: #2196f3;
}
@media screen and (max-width: 450px) {
  #botoes {
    display: flex;
    flex-direction: column;
  }
}