style.css

 *{
    margin:0;
    padding:0;
    box-sizing: border-box;
}
body{
    height:100vh;
    width:100%;
    background:linear-gradient(#2196f3,#45f85d);
    overflow: hidden;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}
.bubbles{
    display:flex;
    width:100%;
    justify-content:space-around;
    position:absolute;
    top:770px;
}
.bubbles span{
    height: 60px;
    width: 60px;
    border-radius: 50%;
    background:rgba(255,255,255,0.15);
    animation: bubble 10s linear infinite;
}
@keyframes bubble{
    0%{
        transform:translateY(-100vh);
        opacity:0;
    }
    25%{
        opacity: 0.5;
    }
    50%{
        opacity:1;
    }
    70%{
        opacity:1;
    }
    100%{
        transform:translateY(0);
        opacity:0;
    }
}
.bubbles span:nth-child(1){
    animation-delay: 2.2s;
}
.bubbles span:nth-child(2){
    animation-delay: 3.5s;
}
.bubbles span:nth-child(3){
    animation-delay: 0.2s;
}
.bubbles span:nth-child(4){
    animation-delay: 6s;
}
.bubbles span:nth-child(5){
    animation-delay: 7s;
}
.bubbles span:nth-child(6){
    animation-delay: 4s;
}
.bubbles span:nth-child(7){
    animation-delay: 3s;
}
.container{
    width: 360px;
    padding:15px;
    background:rgba(255,255,255,0.1);
    border-radius:12px;
    box-shadow:0 20px 50px rgba(0, 0, 0, 0.15);
    border-top: 1px solid rgba(255, 255, 255, 0.5);
    border-left: 1px solid rgba(255, 255, 255, 0.5);
}
.container input[type="text"]{
    width: 100%;
    padding:8px;
    font-size:20px;
    outline: none;
    text-align: right;
    height:50px;
    color:#fff;
    background:transparent;
    border: 2px solid rgba(255, 255, 255, 0.5);
}
.container input[type="button"]{
    outline: none;
    border: none;
    font-size:20px;
    cursor: pointer;
    height: 65px;
    color: #fff;
    width: calc(100% / 4 - 5px);
    background:transparent;
    border-radius:12px;
    margin-top: 15px;  
    transition: all 0.3s ease;
}
.container input[type="button"]:hover{
    background:rgba(255,255,255,0.1);
}
.myname{
    width:360px;
    text-align:center;
    padding-bottom: 15px;
    color:white;
    font-family: cursive;
}