Form.css

* 
{
  margin: 0;
  padding: 0;
}
@font-face {
 font-family: 'Open Sans';
 font-style: normal;
 src: local('Open Sans Bold'), local('OpenSans-Bold'), url(http://themes.googleusercontent.com/static/fonts/opensans/v6/k3k702ZOKiLJc3WVjuplzKRDOzjiPcYnFooOUGCOsRk.woff) format('woff');
}
body{
    margin: none;   
    font-family: 'Open Sans', sans-serif;
    background-image: url(https://i.ytimg.com/vi/q22uHBl9qxw/maxresdefault.jpg);
    background-size: cover;
    background-position: 0px 26.3vh; 
}
h1{
    text-align: center;
    font-style: italic;
    font-size: 50px;
    color: #ffffff;
    text-shadow: 0 0 5px #ffffff, 0 0 10px #ffffff, 0 0 20px #ffffff, 0 0 40px #ff00de, 0 0 80px #ff00de, 0 0 90px #ff00de, 0 0 100px #ff00de, 0 0 150px #ff00de;
}

header{
    padding: 5vh;
    padding-bottom: 1vh;
    background-color: #0B0B3B;
    position: sticky;
    top: 0;
    z-index: 98;
}
.start{
    display: flex;
    justify-content:space-around;
    align-items: center;
    color: #ffffff;
    font-style: italic;
    font-size: 25px;
    text-shadow: 0 0 5px #ffffff, 0 0 10px #ffffff, 0 0 20px #ffffff, 0 0 40px #ff00de, 0 0 80px #ff00de, 0 0 90px #ff00de, 0 0 100px #ff00de, 0 0 150px #ff00de;
    height: 10vh;
}
li{
    display: block;
    margin: 5px;
    
}
a{
    text-decoration: none;
    color: white;
}
.menu-item{
    display: block;
    position: fixed;
    top: 110px
}
.sub-menu{
    overflow: hidden; /* если выходит за границы, то скрывается */
    height: 0;
    opacity: 0; /* прозрачность */
    transition: all 0.5s ease-in;
    z-index: 10;
    background-color: #0B0B3B;
    border-radius: 10px;
}
.for-menu{
    padding: 5px;  
}


.center{
    display: flex;
    align-items: center;
    width: 70%;
    height: 100%;
     background-image: linear-gradient(to top, #7028e4 0%, #e5b2ca 100%);
    margin: auto;
}

* {box-sizing: border-box;}
.transparent {
    position: relative;
    max-width: 400px;
    padding: 20px 50px;
    margin: auto;
    margin-bottom: 5px;
    margin-top: 5px;
    background-image: url(ForFon.png);
    background-size: 400%;
    border-radius: 20px;
}
.form-inner {position: relative;}
.form-inner h3 {
    position: relative;
    margin-top: 0;
    color: white;
    font-weight: 300;
    font-size: 26px;
    text-transform: uppercase;
}
.form-inner label {
    display: block;
    padding-left: 15px;
    color: rgba(255,255,255,.6);
    text-transform: uppercase;
    font-size: 14px;
}
.form-inner input {
    display: block;
    width: 100%;
    padding: 0 15px;
    margin: 10px 0 15px;
    border-width: 0;
    line-height: 40px;
    border-radius: 20px;
    color: white;
    background: rgba(255,255,255,0.2);
}
.form-inner input[type="checkbox"] {
    position: absolute;
    opacity: 0;
}
#custom-checkbox + label {
    position: relative;
    margin: 20px 0;
    text-transform:none;
    cursor: pointer;
}
#custom-checkbox + label:before {
    content: "";
    display: inline-block;
    width: 20px;
    height: 20px;
    margin-right: 10px;
    vertical-align: text-top;
    background: white;
}
#custom-checkbox:checked + label:before {
    background: #1762EE;
}
#custom-checkbox:checked + label:after {
    content: "";
    position: absolute;
    width: 2px;
    height: 2px;
    left: 20px;
    top: 9px;
    background: white;
    box-shadow: 2px 0 0 white, 4px 0 0 white, 4px -2px 0 white, 4px -4px 0 white, 4px -6px 0 white, 4px -8px 0 white;
    transform: rotate(45deg);
}
.form-inner input[type="submit"] {
    background: #E2A9F3;
}