*, *::after, *::before {
  box-sizing: border-box;
}

body {
  font-family: 'Open Sans', sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: #555;
  background: black;
}

.container {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    width: 100vw;
    background-color: #fafafa;
}
.calculator {
    width: 100%;
    max-width: 400px;
    border-radius: 5px;
    padding: 20px;
    box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.1);
    margin-top: 50px;
}

.calculator-keypad {
    margin-top: 50px;
}

.keypad-row {
    display: flex;
    margin-bottom: 20px;
}

.display {
    width: 100%;
    height: 50px;
    border: 1px solid #ccc;
    border-radius: 5px;
    padding: 10px;
    font-size: 20px;
    text-align: right;
}

.keypad-button {
    width: 50%;
    height: 50px;
    border: 1px solid #ccc;
    border-radius: 5px;
    padding: 10px;
    font-size: 20px;
    text-align: center;
}