body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #4158A6;
    font-family: Arial, sans-serif;
    margin: 0;
    position: relative;
    overflow: hidden; /* To hide bubbles that move out of view */
}

.calculator {
    position: relative;
    z-index: 1;
    background-color: #fff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
    width: 340px;
}

.bubble-container {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0; /* Send bubbles behind the calculator */
    overflow: hidden;
}

.bubble {
    position: absolute;
    bottom: 100%;
    width: 40px;
    height: 40px;
    background-color: rgba(255, 255, 255, 0.8);
    border-radius: 50%;
    animation: drop 5s infinite;
    opacity: 0;
}

.bubble:nth-child(2) {
    width: 30px;
    height: 30px;
    animation-duration: 4s;
    left: 10%;
}

.bubble:nth-child(3) {
    width: 50px;
    height: 50px;
    animation-duration: 6s;
    left: 20%;
}
.bubble:nth-child(4) {
    width: 30px;
    height: 30px;
    animation-duration: 4s;
    left: 30%;
}

.bubble:nth-child(5) {
    width: 40px;
    height: 40px;
    animation-duration: 6s;
    left: 80%;
}
.bubble:nth-child(6) {
    width: 30px;
    height: 30px;
    animation-duration: 4s;
    left: 50%;
}

.bubble:nth-child(7) {
    width: 50px;
    height: 50px;
    animation-duration: 6s;
    left: 60%;
}
.bubble:nth-child(8) {
    width: 30px;
    height: 30px;
    animation-duration: 4s;
    left: 7em;
}

.bubble:nth-child(9) {
    width: 50px;
    height: 50px;
    animation-duration: 6s;
    left: 70%;
}
.bubble:nth-child(10) {
    width: 50px;
    height: 50px;
    animation-duration: 6s;
    left: 80%;
}
@keyframes drop {
    0% {
        transform: translateY(-100%);
        opacity: 0;
    }
    10% {
        opacity: 1;
    }
    90% {
        opacity: 1;
    }
    100% {
        transform: translateY(100vh);
        opacity: 0;
    }
}

#display {
    width: 80%;
    padding: 10px;
    font-size: 2em;
    text-align: right;
    border: none;
    outline: none;
    margin-bottom: 10px;
    margin-right: 10px;
    border-radius: 5px;
    background: #F1DEC6;
    box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.1);
}

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

button {
    padding: 20px;
    font-size: 1.2em;
    border: none;
    outline: none;
    border-radius: 5px;
    cursor: pointer;
    background-color: #179BAE;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    transition: background-color 0.3s ease;
}

button:active {
    background-color: #ddd;
}

.zero {
    grid-column: span 2;
}

.equal {
    grid-column: span 2;
    background-color: #FF8343;
    color: white;
}

.equal:active {
    background-color: #45a049;
}