.tree {
    --spacing: 1.5rem;
    --radius: 5px;
    --tree-color: #82D900;
    --parent-padding: 4px;
    padding-left: 0;
}

.tree li {
    display: block;
    position: relative;
    padding-left: calc(2 * var(--spacing) - var(--radius) - 2px);
}

.tree ul {
    margin-left: calc(var(--radius) - var(--spacing));
    padding-left: 0;
}

.tree ul li {
    border-left: 2px solid var(--tree-color);
}

.tree ul li:last-child {
    border-color: transparent;
}

.tree ul li::before {
    content: '';
    display: block;
    position: absolute;
    top: calc(var(--spacing) / -2);
    left: -2px;
    width: calc(var(--spacing) + 2px);
    height: calc(var(--spacing) + 0.2px);
    border: solid var(--tree-color);
    border-width: 0 0 2px 2px;
}

.tree .parent {
    position: relative;
    padding-block: var(--parent-padding);
}

.tree .parent::before {
    content: '';
    position: absolute;
    top: calc(var(--spacing) / 2 - var(--radius) + var(--parent-padding));
    left: calc(var(--spacing) - var(--radius) - 1px);
    width: calc(2 * var(--radius));
    height: calc(2 * var(--radius));
    border-radius: 50%;
    background: var(--tree-color);
    z-index: 1;
}

.tree .parent::after {
    content: '';
    position: absolute;
    display: block;
    width: 2px;
    top: calc(var(--spacing) / 2 + var(--parent-padding));
    left: calc(var(--spacing) - 2px);
    height: 100%;
    background: var(--tree-color);
}

.tree .parent:last-child::after {
    height: 5px;
    bottom: auto;
}

.tree summary {
    display: block;
    cursor: pointer;
}

.tree summary::marker,
.tree summary::-webkit-details-marker {
    display: none;
}

.tree summary:focus {
    outline: none;
}

.tree summary:focus-visible {
    outline: 1px dotted var(--tree-color);
}

.tree li::after,
.tree summary::before {
    content: '';
    display: block;
    position: absolute;
    top: calc(var(--spacing) / 2 - var(--radius));
    left: calc(var(--spacing) - var(--radius) - 1px);
    width: calc(2 * var(--radius));
    height: calc(2 * var(--radius));
    border-radius: 50%;
    background: var(--tree-color);
}

.tree summary::before {
    z-index: 1;
    background: var(--tree-color);
}

.tree .parent>details>summary::before {
    top: calc(var(--spacing) / 2 - var(--radius) + var(--parent-padding));
}

.tree details[open]>summary::before {
    background-position: calc(-2 * var(--radius)) 0;
}

/* 新增：重置 details 的瀏覽器預設間距 */
.tree details {
    padding: 0;
    margin: 0;
}

/* 修改：改用 background 取代 border-left，避免次像素差異 */
.tree .parent::after {
    content: '';
    position: absolute;
    display: block;
    width: 2px;
    top: calc(var(--spacing) / 2 + var(--parent-padding));
    left: calc(var(--spacing) - 2px);
    height: 100%;
    background: var(--tree-color);
    /* 原本是 border-left: 2px solid var(--tree-color) */
}