body {
    font-family: 'Poppins', sans-serif;
    background: linear-gradient(135deg, #6a11cb, #2575fc);
    display: flex;
    flex-direction: column; /* supaya kalkulator & footer sejajar vertikal */
    justify-content: center;
    align-items: center;
    height: 110vh;
    margin: 0;
}

.title {
    color: navajowhite;
    text-align: center;
    margin-top: 20px;
}

.calculator {
    background: rgba(255, 255, 255, 0.15);
    border-radius: 20px;
    padding: 20px;
    box-shadow: 0px 8px 30px rgba(0,0,0,0.3);
    width: 320px;
    backdrop-filter: blur(15px);
}

#display {
    width: 94%;
    height: 60px;
    font-size: 1.8em;
    text-align: right;
    padding: 10px;
    border: none;
    border-radius: 15px;
    margin-bottom: 15px;
    background-color: rgba(255, 255, 255, 0.2);
    color: white;
    outline: none;
}

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

button {
    padding: 15px;
    font-size: 1.3em;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    background-color: rgba(255, 255, 255, 0.2);
    color: white;
    transition: all 0.2s ease;
    backdrop-filter: blur(5px);
}

button:hover {
    background-color: rgba(255, 255, 255, 0.3);
    transform: scale(1.05);
}

button:active {
    transform: scale(0.95);
    box-shadow: 0px 0px 15px #fff;
}

.operator {
    background-color: rgba(255, 215, 0, 0.6);
}

.clear {
    background-color: rgba(255, 0, 0, 0.6);
}

.delete {
    background-color: rgba(255, 140, 0, 0.6);
}

.equal {
    background-color: rgba(0, 255, 127, 0.6);
    grid-row: span 2;
}

footer {
    width: 94%;
    text-align: center;
    padding: 15px;
    margin-top: 20px;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(8px);
    color: white;
    font-size: 0.9em;
    letter-spacing: 0.5px;
    border-radius: 10px;
}