Trouble creating splash Screen

Site URL: https://fife-buttercup-rzmj.squarespace.com/config/

Hi 

I am trying to create a splash screen with the company logo and although I added all the code it didn't work for me. I don't know if I am doing something wrong. 

Site password: 1234

I used this code: 

.splash-wrapper{
  position: fixed;
  z-index: 9999;
  background-color: #ffffff;
  height: 100vh;
  width: 100vw;
  display: flex;
  flex-flow: column nowrap;
  justify-content: center;
  align-items: center;
  animation-name: slideOut;
  animation-fill-mode: forwards;
  animation-duration: 2s;
  animation-delay: 3.375s;
}

@keyframes slideOut{
  from{margin-left: 0vw;}
  to{margin-left: -150vw;}
}

I watched this tutorial to do this that is very good but it didn't work for me: 

Thanks a lot 

Barbara