styles.css

body {
  display: flex;
  justify-content: center;
  flex-direction: column;
  align-items: center;
  height: 98vh;
  background-color: lightblue;
}

.main-container {
  border: 3px solid black;
  background-color: rgb(55, 159, 156);
  padding: 8px;
}

.heading {
  text-align: center;
  border-bottom: 3px solid black;
  font-size: 30px;
}

.calc-screen {
  background-color: lightgray;
  height: 100px;
  margin: 8px;
  border-radius: 24px;
  display: flex;
  align-items: center;
  justify-content: flex-end;
}

.user-input {
  font-size: 70px;
  margin: 5px;
}

button {
  font-size: 25px;
  width: 100%;
  margin: 5px;
  padding: 35px;
  background-color: rgb(153, 229, 13);
  border: none;
  border-radius: 30px;
}

button:hover {
  background-color: rgb(15, 105, 42);
}

#clear,
#del,
#posneg,
#plus {
  padding: 35px 25px 35px 25px;
}

#equals {
  padding: 35px 80px 35px 80px;
}

.button-row {
  display: flex;
  margin: 5px;
}

footer {
  display: flex;
  align-items: center;
  font-size: 25px;
}