body {
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: #111; /* Optional dark background */
}

.all {
    font-family: Arial, sans-serif;
    background-color: hsl(0, 0%, 15%);
    border-radius: 15px;
    max-width: 500px;
    overflow: hidden;
}

#display {
    width: 100%;
    padding: 20px;
    font-size: 5rem;
    text-align: left;
    border: none;
    background-color: hsl(0, 0%, 30%);
    color: white;
    outline: none;
}

#keys {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 25px;
}

button {
    border: none;
    color: white;
    border-radius: 50px;
    height: 100px;
    width: 100px;
    background-color: grey;
    font-size: 3rem;
    font-weight: bold;

}
button:active {
    background-color: white !important;
    color: black !important;
    transform: scale(0.95); /* optional: adds a realistic press effect */

}

button:hover {
    cursor: pointer;
    background-color: orange;
}

/* Number buttons */
.num {
    background-color: #555;
}
.num:hover {
    background-color: #777;
}

/* Operator buttons */
.op {
    background-color: #ff9500;
}
.op:hover {
    background-color: #ffb84d;
}

/* Equal button */
.equal {
    background-color: #2ecc71;
}
.equal:hover {
    background-color: #55d98d;
}

/* Clear button */
.clear {
    background-color: #e74c3c;
}
.clear:hover {
    background-color: #ff6b5a;
}