body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    font-family: 'Roboto', sans-serif;
    background-color: #179d92;
}

.calculator {
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0px 0px 20px 0px rgba(0, 0, 0, 0.1);
    max-width: 400px;
}

.calculator-screen {
    width: 100%;
    height: 80px;
    background-color: #2c1515;
    border: none;
    color: white;
    font-size: 2.5rem;
    text-align: right;
    padding: 0 20px;
    box-sizing: border-box;
}

.calculator-keys {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 20px;
    background-color: #e0e0e0;
}

button {
    height: 60px;
    font-size: 1.5rem;
    border: none;
    border-radius: 5px;
    background-color: white;
    box-shadow: 0px 5px 10px 0px rgba(0, 0, 0, 0.1);
    transition: background-color 0.3s ease;
    cursor: pointer;
}

button.operator {
    background-color: #f39c12;
    color: white;
}

button.operator:hover {
    background-color: #e67e22;
}

button.equal-sign {
    background-color: #2ecc71;
    color: white;
}

button.equal-sign:hover {
    background-color: #27ae60;
}

button.all-clear {
    background-color: #e74c3c;
    color: white;
}

button.all-clear:hover {
    background-color: #c0392b;
}

button:active {
    box-shadow: none;
    transform: translateY(2px);
}

button:focus {
    outline: none;
}