/* General Page Styling */
body {
    background-color: #1e1e2e;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

/* Main Calculator Container */
.calculator {
    background-color: #2b2b3b;
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0px 10px 25px rgba(0, 0, 0, 0.4);
    width: 320px;
}

/* Display Screen Input */
#display {
    width: 100%;
    height: 60px;
    background-color: #181825;
    border: none;
    border-radius: 8px;
    color: #ffffff;
    font-size: 28px;
    text-align: right;
    padding: 10px;
    box-sizing: border-box;
    margin-bottom: 20px;
}

/* Buttons Grid Layout (4 Columns) */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

/* Individual Button Styling */
button {
    height: 55px;
    font-size: 20px;
    border: none;
    border-radius: 8px;
    background-color: #3b3b4f;
    color: #ffffff;
    cursor: pointer;
    transition: background-color 0.2s ease, transform 0.1s ease;
}

/* Interactive Hover & Click Feedback */
button:hover {
    background-color: #4b4b63;
}

button:active {
    transform: scale(0.96);
}

/* Operator & Action Button Highlights */
.operator {
    background-color: #89b4fa;
    color: #11111b;
    font-weight: bold;
}

.operator:hover {
    background-color: #b4befe;
}

.clear {
    background-color: #f38ba8;
    color: #11111b;
    font-weight: bold;
}

.clear:hover {
    background-color: #f5c2e7;
}