style.css

@import url('https://fonts.googleapis.com/css?family=Poppins:300,400,500,600,700,800,900&display=swap');
*
{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
    scroll-behavior: smooth;
}
body
{
    min-height: 100vh;
    overflow-x: hidden;
    background: linear-gradient(#2b1055,#7597de)
}
header
{
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    padding: 30px 100px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 10000;
}
header .logo
{
   color: #fff;
   font-weight: 700;
   text-decoration: none; 
   font-size: 2em;
   text-transform: uppercase;
   letter-spacing: 2px;
   z-index: 10000;
}
header ul
{
    display: flex;
    justify-content: center;
    align-items: center;
}
header ul li 
{
    list-style: none;
    margin-left: 20px;
}
header ul li a 
{
    text-decoration: none;
    padding: 6px 15px;
    color: #fff;
    border-radius: 20px;
}
header ul li a:hover ,
header ul li a.active
{
    background:#fff;
    color: #2b1055;

}
section
{
    position: relative;
    width: 100%;
    height: 100vh;
    padding: 100px;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
}
section::before
{
    content: '';
    position: absolute;
    bottom: 0;
    width: 100%;
    height: 100px;
    background: linear-gradient(to top,#1c0522,transparent);
    z-index: 1000;
}
section img
{
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    pointer-events: none;
}
section img#moon
{
    mix-blend-mode: screen; 
}
section img#mountains_front
{
    z-index: 10;
}
#text
{
    position: absolute;
    right: -350px;
    color: #fff;
    white-space: nowrap;
    font-size: 11.5vw;
    z-index: 9;
    transform: translateY(100px);
}
#btn
{
    text-decoration: none;
    display: inline-block;
    padding: 8px 30px;
    border-radius: 40px;
    background: #fff;
    color: #2b1055;
    font-size: 1.5em;
    z-index: 9;
    transform: translateY();
}
.sec 
{
    position: relative;
    padding: 100px;
    background: #1c0522;
}
.sec h2 
{
    font-size: 3.5em;
    margin-bottom: 10px;
    color: #fff;
}
.sec p
{
    font-size: 1.2em;
    color: #fff;
}