/* General Styles */
body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f4f4f4;
    font-family: 'Arial', sans-serif;
}

/* Calculator Container */
.calculator {
    width: 320px;
    border: 1px solid #ccc;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    background-color: #fff;
}

/* Display Screen */
.display {
    background-color: #333;
    color: #fff;
    text-align: right;
    padding: 20px;
    font-size: 2em;
    border-bottom: 1px solid #ccc;
    box-sizing: border-box;
    height: 80px;
    line-height: 40px;
    overflow-y: hidden;
}

/* Buttons Container */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(5, 80px);
}

/* Button Styles */
.button {
    background-color: #e0e0e0;
    border: 1px solid #ccc;
    font-size: 1.5em;
    cursor: pointer;
    outline: none;
    transition: background-color 0.3s ease;
}

.button:hover {
    background-color: #d4d4d4;
}

.button:active {
    background-color: #ccc;
}

.equal {
    background-color: #4caf50;
    color: #fff;
    grid-row: span 2;
}

.equal:hover {
    background-color: #45a047;
}

.equal:active {
    background-color: #388e3c;
}

/* Wide button for '0' */
.zero {
    grid-column: span 2;
}