* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Segoe UI", sans-serif;
}

body {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: radial-gradient(circle at top, #1e1e2f, #0a0a12);
}

/* Calculator body */
.calculator {
    width: 320px;
    padding: 20px;
    border-radius: 20px;
    background: rgba(255, 255, 255, 0.08);
    backdrop-filter: blur(20px);
    box-shadow:
        0 0 20px rgba(0, 255, 255, 0.2),
        0 0 60px rgba(0, 140, 255, 0.15);
}

/* Display */
#display {
    width: 100%;
    height: 70px;
    border-radius: 12px;
    border: none;
    outline: none;
    text-align: right;
    padding: 15px;
    font-size: 2rem;
    color: #fff;
    background: rgba(0, 0, 0, 0.4);
    box-shadow: inset 0 0 10px rgba(0, 255, 255, 0.3);
    margin-bottom: 15px;
}

/* Buttons grid */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}

/* Buttons */
button {
    height: 60px;
    border-radius: 14px;
    border: none;
    font-size: 1.3rem;
    font-weight: 600;
    cursor: pointer;
    color: #fff;
    background: rgba(255, 255, 255, 0.12);
    box-shadow:
        0 0 10px rgba(0, 255, 255, 0.2),
        inset 0 0 10px rgba(255, 255, 255, 0.05);
    transition: all 0.25s ease;
}

button:hover {
    transform: scale(1.05);
    box-shadow:
        0 0 20px rgba(0, 255, 255, 0.6),
        inset 0 0 10px rgba(255, 255, 255, 0.15);
}

/* Operator buttons */
.orange {
    background: linear-gradient(135deg, #ff9800, #ff5722);
    box-shadow: 0 0 15px rgba(255, 152, 0, 0.6);
}

.orange:hover {
    box-shadow: 0 0 25px rgba(255, 152, 0, 1);
}

/* Responsive */
@media (max-width: 400px) {
    .calculator {
        width: 95%;
    }

    button {
        height: 55px;
        font-size: 1.1rem;
    }

    #display {
        height: 60px;
        font-size: 1.7rem;
    }
}