* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: system-ui, -apple-system, Segoe UI, Roboto, 'Helvetica Neue', Arial
}

body {
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #f3f4f6
}

.calculator {
    background: #1f2937;
    color: #fff;
    padding: 16px;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
    width: 360px
}

.display {
    height: 64px;
    background: rgba(255, 255, 255, 0.06);
    display: flex;
    align-items: center;
    justify-content: flex-end;
    padding: 0 12px;
    border-radius: 8px;
    font-size: 2rem;
    margin-bottom: 12px;
    overflow: hidden
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px
}

button {
    background: #111827;
    border: none;
    color: inherit;
    padding: 18px;
    font-size: 1.1rem;
    border-radius: 8px;
    cursor: pointer;
    box-shadow: inset 0 -4px rgba(0, 0, 0, 0.2)
}

button:hover {
    filter: brightness(1.05)
}

button:active,
.active {
    transform: translateY(1px);
    filter: brightness(0.95)
}

button[data-action="equals"] {
    background: #10b981;
    color: #fff
}

button[data-action="clear"] {
    background: #ef4444
}

button[data-action="delete"] {
    background: #f59e0b
}

.span-two {
    grid-column: span 2
}

@media(max-width:420px) {
    .calculator {
        width: 92vw
    }
}