body {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 100vh;
    font-family: 'Segoe UI', sans-serif;

    background: linear-gradient(-45deg, #ff9a9e, #fad0c4, #fbc2eb, #a6c1ee);
    background-size: 400% 400%;
    animation: gradientBG 8s ease infinite;
}

/* animated bg */
@keyframes gradientBG {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

.title {
    color: #ff4d6d;
    font-family: 'Pacifico', cursive;
    margin-bottom: 15px;
    letter-spacing: 2px;
}

/* glass effect */
.calculator {
    width: 280px;
    padding: 20px;
    border-radius: 25px;

    background: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(15px);

    box-shadow: 0 10px 40px rgba(0,0,0,0.3);

    animation: float 3s ease-in-out infinite;
}

/* floating animation */
@keyframes float {
    0%,100% { transform: translateY(0px); }
    50% { transform: translateY(-10px); }
}

/* display glow text */
#display {
    width: 100%;
    height: 60px;
    font-size: 26px;
    border-radius: 15px;
    border: none;
    margin-bottom: 15px;
    padding: 10px;
    text-align: right;

    background: rgba(255,255,255,0.3);
    color: #ff4d6d;
    font-family: 'Orbitron', sans-serif;
    letter-spacing: 2px;
    text-shadow: 0 0 8px #ff6b81;

    box-shadow: inset 0 0 10px rgba(0,0,0,0.2);
}

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

/* unique rounded + glow buttons */
button {
    height: 60px;
    border: none;
    border-radius: 20px;
    font-size: 18px;
    cursor: pointer;

    background: rgba(255, 182, 193, 0.7);
    color: white;

    box-shadow: 
        0 5px 15px rgba(255, 105, 135, 0.5),
        inset 0 -3px 5px rgba(0,0,0,0.2);

    transition: all 0.2s ease;
}

/* hover glow */
button:hover {
    transform: scale(1.1);
    box-shadow: 
        0 0 20px rgba(255, 105, 180, 0.9),
        0 5px 20px rgba(255, 105, 135, 0.6);
}

/* press effect */
button:active {
    transform: scale(0.95);
}

/* special buttons */
.equal {
    grid-row: span 2;
    background: linear-gradient(135deg, #a18cd1, #fbc2eb);
}

.zero {
    grid-column: span 2;
}
.credit {
    text-align: center;
    font-size: 12px;
    font-family: 'Quicksand', sans-serif;
    color: #ff6b81;
    margin-top: 10px;
    letter-spacing: 1px;
}

.credit a {
    color: #ff4d6d;
    text-decoration: none;
    font-weight: bold;
}

.credit a:hover {
    text-decoration: underline;
}