*{ 
  margin: 0px;
  padding: 0px;
  box-sizing: border-box;
}
html {
  max-width: 100%;
  overflow: hidden;
  font-size: 16px
}

h1, h3, h4, h5, a{ font-family: "fRegu", sans-serif; text-decoration: none; font-optical-sizing: auto;}
h1 { font-weight: 700; font-size: 2rem; }

h3 { font-weight: 400; font-size: 1.6rem; }
h4 { font-weight: 400; font-size: 1rem; color: #fff; }
h5 { font-weight: 400; font-size: 1.25rem;}

body {
  display: flex;
  justify-content: space-between;
}
#sidebar {
  height: 100vh;
  width: 10%;
  min-width: 200px;
  z-index: 1;
  background-color: #ffffff;
  border-right: 8px solid #1b95cd;
  display: flex;
  flex-direction: column;
  flex-wrap: nowrap;
  justify-content: space-around;
  align-items: center;
  align-content: normal;
}
#sidebar div {
  width: 100%;
  display: flex;
  flex-direction: column;
  text-align: center;
}
.sub .link:nth-of-type(1) {background-color: #fbfbfb}
.sub .link:nth-of-type(2) {background-color: #eeeeee}
.sub .link:nth-of-type(3) {background-color: #dedede}
.sub .link:nth-of-type(4) {background-color: #d7d6d6}
.sub .link a{
  vertical-align: sub;
  height: 50px;
  margin: 0 10px;
}
.sub .link h3 {
  color: #000;
  font-size: 1.5rem;
  font-weight: 500;
  text-align: center;
}
.sub .link a:hover h3 {
  font-size: 1.9rem;
  font-weight: 600;
  color: #000;
}
.hidden {
  display: none;
  visibility: hidden;
}
@media (hover:hover) {
  .sub .link a {
  transition: height 1s ease 0s;
  }
  .sub .link a:hover {
  background-color: #222;
  box-shadow: 1px 3px 15px rgba(0, 0, 0, 0.5);
  border-radius: 10px;
  height: 100px;
}
.sub .link a:hover .hidden{
  display: block;
  visibility: visible;
  background-color: #222;
}
.sub .link a:hover h3{ color: #fff; }
  li:hover {
    font-weight: 600;
    background-color: #222;
    animation: pulse 0.3s ease 0s 1 normal forwards;
  }
  li:hover a { color: #fff;}
}
@keyframes pulse {
	0% { transform: scale(1); }
	50% { transform: scale(1.1); }
	100% { transform: scale(1);}
}
main {
  width: 90%;
  margin-left: 20px;  
  height: 100vh;
  z-index: 0;
  background: linear-gradient(180deg,#404040 10%,#2a2a2a 95%);
  position: relative;
  margin: 0 auto;
  overflow: hidden; 
}
main img {
  --duration: 40s;
  --name: waterfall-1;
  position: absolute;
  top: 0;
  left: 0;
  max-width: 35vw;
  transform: translateY(200vh);
  animation: var(--name) var(--duration) linear infinite;
  box-shadow: 1px 3px 15px rgba(0, 0, 0, 0.5);
  z-index: 1;
  pointer-events: none;
  }
main img:nth-of-type(4n-2) {
  --name: waterfall-1;
  --duration: 15s;
}
main img:nth-of-type(4n-0) {
  --name: waterfall-3;
  --duration: 20s;
}
main img:nth-of-type(4n-1) {
  --name: waterfall-2;
  --duration: 25s;
}
main img:nth-of-type(4n-3) {
  --name: waterfall-1;
  --duration: 30s;
}
@keyframes waterfall-3
   {
    from {
      transform: translateY(-200vh) ;
    }
    to {
      transform: translateY(210vh) ;
    }
  }
  @keyframes waterfall-2
   {
    from {
      transform: translateY(-150vh) ; 
    }
    to {
      transform: translateY(190vh) ;
    }
  }
  @keyframes waterfall-1
   {
    from {
      transform: translateY(-100vh);
    }
    to {
      transform: translateY(110vh);
    }
  }
  @keyframes blink {
    0% {
      opacity: 0;
    }
  }
@media (max-width: 700px) {
  main img {
    min-width: 150px;
  }
}