style.css

* {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  box-sizing: border-box;
}

body {
  background-color: #ffffff;
  min-height: auto;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: #131313;
}

.container {
  width: auto;
  height: auto;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 17px;
  border-radius: 9px;
  user-select: none;
}

#Display-area {
  width: 100%;
  margin: 3vh 0;
  display: grid;
  grid-template-columns: 100%;
  grid-template-rows: repeat(2, minmax(40px, auto));
  word-wrap: break-word;
  border-bottom: 1px rgba(128, 128, 128, 0.116) solid;
}

#Display-area .currentInput {
  /* display: flex; */
  text-align: right;
  height: 8vh;
  color: white;
  font-size: xx-large;
  line-height: 2;
  word-wrap: break-word;
  font-weight: bold;
}

#Display-area .answerScreen {
  text-align: right;
  color: rgba(150, 150, 150, 0.87);
  height: 7px;
  line-height: 3;
  font-size: larger;
}

.keypad-btns {
  display: grid;
  grid: repeat(5, 90px) / repeat(4, 130px);
  grid-row-gap: 20px;
  grid-column-gap: 20px;
}

.keypad-btns button {
  outline: none;
  border: none;
  border-radius: 8px;
  background-color: #474b6b;
  color: #fff;
  font-size: x-large;
  font-weight: bold;
}

.keypad-btns .fun_btn {
  color: #000;
  background: #95a7ff;
  font-weight: bold;
}

button:hover{
  opacity: 0.8;
}

#clear {
  background: #ff8052;
}

@media only screen and (max-width: 600px) {
  body {
    background-color: #131313;
    align-items: flex-start;
  }
}