.tree {
    --spacing: 1.5rem;
    --radius: 8px;
}

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

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

.tree ul li {
    border-left: 2px solid rgb(33, 33, 33);
}

.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) + 1px);
    border: solid rgb(33, 33, 33);
    border-width: 0 0 2px 2px;
}

.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 #000;
}

.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: rgb(105, 105, 130);
}

.tree summary::before {
    content: '+';
    z-index: 1;
    background: rgb(75, 75, 100);
    color: #ff8600;
    line-height: calc(2 * var(--radius) - 2px);
    text-align: center;
    font-weight: bold;
}

.tree details[open] > summary::before {
    content: '−';
}