CSS中樹的單詞有哪些？

.tree {
margin: 0;
padding: 0;
list-style: none;
}
.tree li {
margin: 0;
padding: 10px 16px;
position: relative;
}
.tree li:before, .tree li:after {
content: '';
position: absolute;
top: 0;
right: 50%;
border-top: 1px solid #ccc;
width: 50%;
height: 1em;
}
.tree li:after {
right: auto;
left: 50%;
border-left: 1px solid #ccc;
}
.tree li:first-child:before {
border: none;
}
.tree .active:before, .tree .active:after {
border-color: #008000;
}
.tree li:last-child:before {
height: auto;
bottom: 0;
top: 0;
border-bottom: 1px solid #ccc;
}
.tree li:last-child:before {
height: auto;
bottom: 0;
top: 0;
border-bottom: 1px solid #ccc;
}
.tree li:last-child:after {
display: none;
}
.tree li.parent_li >span {
cursor: pointer;
position: relative;
left: -6px;
}
.tree li.parent_li:before {
content: '';
position: absolute;
left: -45px;
bottom: 50px;
border-left: 1px solid #ccc;
border-bottom: 1px solid #ccc;
height: 25px;
width: 35px;
top: 50%;
z-index: 1;
}
.tree li.parent_li:after {
content: '';
position: absolute;
left: -17px;
border-left: 1px solid #ccc;
border-top: 1px solid #ccc;
top: 12px;
height: 50%;
width: 20px;
z-index: 1;
}
.tree li.parent_li >span:before {
content: '';
position: absolute;
border-top: 1px solid #ccc;
top: 14px;
left: -18px;
width: 18px;
height: 0;
}
.tree li.parent_li >span:after {
content: '';
position: absolute;
border-left: 1px solid #ccc;
top: 16px;
left: -20px;
height: 0;
width: 0;
}

CSS中樹的單詞主要是列表相關的樣式，通過設置列表項和子項的樣式實現樹形結構。其中，parent_li表示父級列表項的樣式。