这是一款jQuery和CSS3带变形特效的固定导航菜单。该导航菜单开始时固定在页面左上角，当用户向下滚动时，导航菜单以水滴变形的方式转换为圆形菜单，然后固定在页面的左上角位置。

HTML结构

该导航菜单的主菜单HTML结构如下：

<nav>
  <div id="drop">
    <div>
      <span></span>
      <span></span>
      <span></span>
    </div>
  </div>
</nav>

然后创建全屏导航菜单。

<ul>
  <li>Home</li>
  <li>Portfolio</li>
  <li>Jobs</li>
  <li>Contact</li>
  <li>About</li>
</ul>

CSS样式

为导航菜单添加下面的CSS样式。

#drop, nav { background-color: #f8f8f8 }
nav {
  width: 90%;
  height: 90px;
  padding: 0 5%;
  position: relative;
  justify-content: flex-start;
  align-items: center
}
  
nav~ul {
  position: absolute;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  left: 1%;
  right: 1%;
  opacity: 0;
  visibility: hidden;
  z-index: 2;
  list-style: none;
  transition: 0s
}
  
nav~ul>li {
  color: #70f;
  padding: 10px;
  cursor: pointer;
  font-size: 30px
}
  
nav~ul>li:hover { filter: brightness(200%) }
  
nav.open~ul {
  transition: .75s ease-in-out;
  visibility: visible;
  opacity: 1
}
  
#drop {
  cursor: pointer;
  position: fixed;
  width: 70px;
  height: 70px;
  border-radius: 0 50% 50%;
  transform: rotate(45deg);
  transition: border-radius .5s
}
  
nav.open>#drop {
  transition: .5s ease-in-out;
  box-shadow: 0 0 0 1000px #f8f8f8, inset 0 0 0 20px #f8f8f8;
  position: relative
}
  
#drop.active {
  border-radius: 50%;
  animation: drop .3s forwards
}
  
#drop>div {
  transform: rotate(-45deg);
  height: 100%;
  width: 100%;
  flex-direction: column;
  justify-content: center;
  align-items: center
}
  
#drop span {
  display: block;
  background-color: #70f;
  width: 40px;
  height: 3px;
  margin: 5px 0;
  transition: .5s
}
  
#drop span.open:nth-child(1) { transform: rotate(45deg) translate(5px, 5px) }
  
#drop span.open:nth-child(2) { transform: rotate(-45deg) translate(5px, -5px) }
  
#drop span.open:nth-child(3) { opacity: 0 }
  
@keyframes 
drop { 0% {
transform:translateY(0) rotate(45deg)
}
50% {
transform:translateY(30px) rotate(45deg)
}
100% {
transform:translateY(10px) rotate(45deg)
}
}