body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
    font-family: 'Roboto Mono', monospace;
}

.calculator {
    background: rgba(255, 255, 255, 0.08);
    backdrop-filter: blur(15px);
    padding: 20px;
    border-radius: 20px;
    box-shadow: 0 8px 25px rgba(0,0,0,0.3);
    width: 320px;
    animation: fadeIn 0.5s ease-in-out;
}

#display {
    width: 100%;
    height: 60px;
    font-size: 1.8em;
    text-align: right;
    margin-bottom: 15px;
    border: none;
    border-radius: 12px;
    padding: 10px;
    background: rgba(255,255,255,0.15);
    color: #fff;
    outline: none;
}

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

button {
    padding: 15px;
    font-size: 1.2em;
    border: none;
    border-radius: 12px;
    background: rgba(255,255,255,0.15);
    color: #fff;
    cursor: pointer;
    box-shadow: inset 2px 2px 5px rgba(255,255,255,0.2),
                inset -2px -2px 5px rgba(0,0,0,0.3);
    transition: all 0.2s ease;
}

button:hover {
    transform: scale(1.05);
    background: rgba(255,255,255,0.25);
}

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

.equal:hover {
    background: #3b9be0;
}

.zero {
    grid-column: span 2;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}