/* Global Styles */
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #1e1e1e;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    color: #fff;
}

.container {
    background: #2a2a2a;
    padding: 30px;
    border-radius: 15px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.3);
    width: 280px;
    text-align: center;
}

h1 {
    margin-bottom: 20px;
    font-size: 30px;
    color: #fff;
}

input {
    width: 90%;
    height: 50px;
    padding: 0 10px;
    margin-bottom: 20px;
    font-size: 32px;
    text-align: right;
    background-color: #333;
    border: 2px solid #444;
    border-radius: 10px;
    color: #fff;
    outline: none;
}

input:focus {
    border-color: #007BFF;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

button {
    padding: 20px;
    background-color: #3b3b3b;
    color: #fff;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    font-size: 20px;
    transition: background-color 0.3s, transform 0.1s;
}

button:hover {
    background-color: #555;
    transform: scale(1.05);
}

button:active {
    transform: scale(1);
}

button:focus {
    outline: none;
}

button.operator {
    background-color: #007BFF;
}

button.operator:hover {
    background-color: #0056b3;
}

button.equals {
    background-color: #28a745;
}

button.equals:hover {
    background-color: #218838;
}

button.clear {
    background-color: #dc3545;
}

button.clear:hover {
    background-color: #c82333;
}

/* Media Query for Mobile Devices */
@media (max-width: 480px) {
    .container {
        width: 90%;
        padding: 20px;
    }

    h1 {
        font-size: 24px;
    }

    input {
        font-size: 28px;
        height: 45px;
    }

    button {
        font-size: 18px;
        padding: 15px;
    }

    .buttons {
        grid-template-columns: repeat(4, 1fr);
        gap: 8px;
    }
}