* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  min-height: 100vh;
  background-color: #efeff2;
  display: flex;
  justify-content: center;
  align-items: center;
}
.cal {
  width: 300px;
  height: 500px;
  box-shadow: 5px 5px 5px rgba(0, 0, 0, 0.3);
  border-radius: 12px;
  overflow: hidden;
  background-color: #22252d;
}
form input {
  width: 100%;
  height: 150px;
  border: none;
  border-radius: 12px;
  font-size: 2rem;
  padding: 1rem;
  color: #fff;
  background-color: #000;
  text-align: right;
  pointer-events: none;
}
.main {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  padding: 20px;
}
button {
  flex: 1 0 21%;
  margin: 5px 0;
  width: 60px;
  height: 52px;
  font-size: 22px;
  font-weight: 600;
  border-radius: 5px;
  cursor: pointer;
}
.btn-yellow {
  background-color: #ed964b;
  color: #fff;
}
.btn-grey {
  background-color: #e0e0e0;
}
.btn-equal {
  background-color: #539d53;
  color: #fff;
}
.btn-clear {
  background-color: #d03b3b;
  color: #fff;
}
.btn-del{
  background-color: #d03b3b;
color: #fff;  
}