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

body {
  background-image: url('image/cal.jpg');
  background-repeat: no-repeat;
  background-size: cover;
  height: 90vh;
}

@media screen and (max-width: 768px) {
  body {
    background-image: url('image/calc.jpg');
    background-position: calc(50% - 50px);
  }
}

.btn,
.clear {
  margin: 0.3%;
  width: 16%;
  height: 60px;
  box-shadow: 0 0 5px 0 #bbb;
}

.clear {
  border: none;
  background-color: #ffff;
  border-radius: 5px;
  box-shadow: 0 0 5px 0 #bbb;
}

input {
  outline: 1px solid rgb(218, 228, 243);
  border: none;
  box-shadow: 0 0 5px 0 #bbb;
}

.main {
  margin: 4rem auto;
  text-align: center;
  align-items: center;
  justify-content: center;
}

#calc-board {
  align-items: center;
}

.reset {
  font-size: 15px;
  font-weight: bolder;
}