style.css

*{
    margin: 0;
    padding: 0;
    font-family: sans-serif;
}
.container{
    width: 100%;
    height: 100vh;
    background: url(images/background.png) no-repeat center center/cover;
    position: relative;
    overflow: hidden;
}
.navbar{
    width: 90%;
    height: 15%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin: auto;
}
.logo{
    width: 150px;
    cursor: pointer;
}
.btn{
    color: #fbfcfd;
    padding: 10px 25px;
    background: transparent;
    border: 1px solid #fff;
    border-radius: 20px;
    outline: none;
    cursor: pointer;
}
.content{
    color: #fbfcfd;
    position: absolute;
    top: 50%;
    left: 8%;
    transform: translateY(-50%);
    z-index: 1;
}
small{
    font-size: 20px;
}
h1{
    font-size: 100px;
    margin: 15px 0px 30px;
    line-height: 80px;
}
.side-bar{
    width: 50px;
    height: 100vh;
    background: linear-gradient(#00545d, #000729);
    position: absolute;
    right: 0;
    top: 0;
}
.menu{
    display: block;
    width: 30px;
    margin: 58px auto 0;
    cursor: pointer;
}
.social-links{
    width: 50px;
    text-align: center;
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
}
.usefull-links{
    width: 50px;
    text-align: center;
    position: absolute;
    bottom: 20px;
}
.social-links img, .usefull-links img{
    width: 30px;
    margin: 5px auto;
    cursor: pointer;
}
.bubbles{
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-around;
    position: absolute;
    bottom: -60px;
}
.bubbles img{
    animation: bubble 5s linear infinite;
}

@keyframes bubble {
    0%{
        transform: translateY(0);
        opacity: 0;
    }
    20%{
        opacity: 1;
    }
    40%{
        opacity: 1;
    }
    60%{
        opacity: 1;
    }
    80%{
        opacity: 1;
    }
    100%{
        transform: translateY(-80vh);
        opacity: 0;
    }
}

.bubbles img:nth-child(1){
    animation-delay: 2s;
    width: 45px;
}
.bubbles img:nth-child(2){
    animation-delay: 1s;
    width: 35px;
}
.bubbles img:nth-child(3){
    animation-delay: 3.5s;
    width: 55px;
}
.bubbles img:nth-child(4){
    animation-delay: 4.5s;
    width: 40px;
}
.bubbles img:nth-child(5){
    animation-delay: 2.5s;
    width: 55px;
}
.bubbles img:nth-child(6){
    animation-delay: 6s;
    width: 45px;
}
.bubbles img:nth-child(7){
    animation-delay: 7s;
    width: 60px;
}