如何结合第一个孩子：悬停和另一个元素有：之前？

Question

当鼠标悬停在列表项的:before上时，我希望对first-child元素生效，以便代码

li:first-child:hover ul:before { Code here }

要更清楚地看到here中的代码或参见下面的

（我希望对.sub1-ul:before）

产生效果

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* { 
    box-sizing: border-box;
    text-decoration: none;
    list-style-type: none
}

nav.nav-menu {
    width:100%;
    margin: 0 auto;
    z-index: 2000;
}

ul.menu-wrapper {
    position: relative;
    width: 770px;
    height: 90px;
    padding-left: 100px;
    padding-top: 15px;
    margin: 0px auto;
    z-index: 2000;
}

li.nav-item {
    position: relative;
    float: left;
    margin-left: 30px
}

li.nav-item > a {
    display: inline-block;
    width: 150px;
    height: 50px;
    padding-top: 11px;
    background-color: #3498DB;
    color: #fff;
    text-align: center;
    font-weight: 600;
    font-size: 19px;
    border: 1px solid #5aabe1;
    -webkit-transition: background-color 400ms, color 700ms ease-out;
       -moz-transition: background-color 400ms, color 700ms ease-out;
            transition: background-color 400ms, color 700ms ease-out
}

li.nav-item:hover > a {
    background-color: #fffffc;
    color: #3498db
}

/* ========== START SUB1 ========== */

.sub1-ul:before {
    content: "";
    display: inline-block;
    position: relative;
    width: 0px;
    top: 15px;
    left: 30px;
    border-width: 0px 15px 15px 0px;
    border-color: #0f0 #0F8FD3 transparent #000;
    border-style: solid solid solid solid;
    transform: rotate(-45deg)
}

.sub1-ul li:first-child:hover .sub1-ul:before {
    content: "";
    display: inline-block;
    position: relative;
    width: 0px;
    top: 15px;
    left: 3px;
    border-width: 0px 15px 15px 0px;
    border-color: #0f0 #000 transparent #000;
    border-style: solid solid solid solid;
    transform: rotate(-45deg)
}

.sub1-ul {
    position: absolute;
    top: 50px;
    width: 100%;
    height: 0;
    margin-top:-10px ;
    visibility: hidden;
    overflow: hidden;
    opacity: 0;
    z-index: 9999;
    -webkit-transition: all .2s linear;
       -moz-transition: all .2s linear;
            transition: all .2s linear
}

li.nav-item:hover .sub1-ul {
    height: auto;
    visibility: visible;
    overflow: visible;
    opacity: 1
}

.sub1-item {
    position: relative;
    top: -1px;
    left: -36%;
    width: 150px;
    margin-top: 3px;
    -webkit-transition:margin-left 200ms linear;
       -moz-transition:margin-left 200ms linear;
            transition:margin-left 200ms linear
}

.sub1-item:hover {
    margin-left: 4px;
}

.sub1-item .sub1-a {
    display: inline-block;
    width: 150px;
    height: 50px;
    padding-top: 15px;
    background-color: #0F8FD3;
    text-align: center;
    color: #fff;
    font-size: 17px;
    border-left: 6px solid #4C4C4C;
    -webkit-transition: background-color 400ms,
                        border-left-color 400ms,
                        padding-left 200ms linear;
    
       -moz-transition: background-color 400ms,
                        border-left-color 400ms,
                        padding-left 200ms linear;
    
            transition: background-color 400ms,
                        border-left-color 400ms,
                        padding-left 500ms linear
}

.sub1-item:hover .sub1-a {
    padding-left: 6px;

    border-left-color: #e67e22;   
}

/* ========== START SUB2 ========== */

.sub2-ul {
    position: absolute;
    top: 0px;
    left: 100%;
    width: 150px;
    padding: 0;
    margin: 0;
    visibility: hidden;
    overflow: hidden;
    opacity: 0;
    -webkit-transition: all 400ms ease;
       -moz-transition: all 400ms ease;
            transition: all 400ms ease
}

.sub1-item:hover .sub2-ul { 
    height: auto;
    visibility: visible;
    overflow: visible;
    opacity: 1
}

.sub2-item {
    position: relative;
    margin-bottom:2px;
}

.sub2-item:hover {
    border-left-color: #4c4c4c
}

.sub2-item .sub2-a {
    display: inline-block;
    width:150px;
    height:50px;
    margin-left: 1px;
    padding-top:15px;
    background-color: #3498DB;
    color: #fff;
    text-align: center;
    font-size: 17px;
    font-weight: normal;
    border-left: 5px solid #e67e22;
    -webkit-transition:all 200ms ease-in-out;
       -moz-transition:all 200ms ease-in-out;
            transition: all 200ms ease-in
}

.sub2-item:hover .sub2-a {
    border-left-color: #4c4c4c
}

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<nav id="sec-nav" class="nav-menu">
  <ul class="menu-wrapper">
    <li class="nav-item"><a href="#"> Menu1 </a>
      <ul class="sub1-ul">

<!-- ===== Want to move before with this list item when mouseover on it =====-->

        <li class="sub1-item">
          <a class="sub1-a" href="#"> sub menu </a>
          <ul class="sub2-ul">
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
          </ul>
        </li>

<!--================  Ens of the list item ========================  -->

        <li class="sub1-item">
          <a class="sub1-a" href="#"> sub menu </a>
          <ul class="sub2-ul">
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
            <li class="sub2-item"><a class="sub2-a" href="#"> sub menu2 </a>
            </li>
          </ul>
        </li>
        <li class="sub1-item"><a class="sub1-a" href="#"> sub menu </a>
        </li>
        <li class="sub1-item"><a class="sub1-a" href="#"> sub menu </a>
        </li>
        <li class="sub1-item"><a class="sub1-a" href="#"> sub menu </a>
        </li>
      </ul>
    </li>
    <li class="nav-item"><a href="#"> Menu2 </a>
    </li>
    <li class="nav-item"><a href="#"> Menu3 </a>
    </li>
  </ul>
</nav>

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