style.css

 /* Reset default browser styles */
 * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* Style for the body */
body {
    background-color: black;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    flex-direction: column;
}

/* Style for the display text */
.display {
    color: #fcfcfc;
    overflow: hidden;
    padding: 20px;
    text-align: right;
    font-size: 2em;
    border-radius: 10px;
    background-color: #401a63;
    width: calc(100% - 40px);
}

/* Style for the background container */
.background {
    background-color: blueviolet;
    padding: 20px;
    border-radius: 10px;
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 100%;
    max-width: 400px;
}

/* Style for the screen container */
.screen {
    width: 100%;
    margin-bottom: 20px;
}

/* Base styles for buttons */
.button {
    background-color: #f87d09;
    background-image: linear-gradient(to right, #eb6f0a, #780adf);
    border: none;
    color: white;
    padding: 15px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 1.2em;
    margin: 5px;
    cursor: pointer;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transition: all 0.3s ease;
    flex: 1 1 30%;
    max-width: 30%;
}

/* Hover effect for buttons */
.button:hover {
    background-image: linear-gradient(to right, #f55e07, #4CAF50);
    box-shadow: 0 6px 8px rgba(0, 0, 0, 0.15);
    transform: translateY(-2px);
}

/* Style for the button containers */
.buttons {
    display: flex;
    flex-wrap: wrap;
    width: 100%;
}

.operator {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
    width: 100%;
}

.number {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
    width: 100%;
}

/* Responsive styles */
@media (max-width: 480px) {
    .button {
        font-size: 1em;
        padding: 10px;
    }

    .display {
        font-size: 1.5em;
        padding: 15px;
    }
}