Custom theme styles for Fargo (http://fargo.io). Adds some usability tweaks like hover states and a border indicating dropping a child vs a sibling. (Some of the rules are webkit specific since I primary use Chrome.) Feel free to use them, or fork and make them your own.

gistfile1.css

/* Hand cursor indicating the "wedge" is clickable. */
.node-icon {
    cursor: pointer !important;
}

/* Keep the line-length of individual nodes from getting too wide. */
.concord-text {
    max-width: 48em;
}

/* Move cursor indicating the node can be moved. */
.concord-node.selected > .concord-wrapper > .node-icon:hover {
    cursor: move !important;
}

/* Better differentiate collapsed wedges from expanded wedges. */
.concord-node.collapsed > .concord-wrapper.type-icon .node-icon.icon-caret-right {
    color: #BE202E !important;
}
.concord-node:not(.collapsed) > .concord-wrapper.type-icon > .node-icon.icon-caret-right {
    -webkit-transform: rotateZ(90deg);
    -webkit-transition-property: -webkit-transform;
    -webkit-transition-duration: 0.25s;
}

/* Hover state for individual node */
.concord-node:not(.selected) > .concord-wrapper:hover {
    background-color: rgba(0,0,222,0.1) !important;
}
/* Show focused nodes in a darker blue (since the plain cursor isn't
always so noticable). */
.concord-node:not(.selected) > .concord-wrapper > .concord-text:focus {
    background-color: rgba(0,0,222,0.2) !important;
}
.concord-node {
    border-left: 1px dotted transparent;
}
.concord-node:hover {
    border-left-color: rgba(85,85,85,0.4);
}

/* Show a border to better indicate where the node being dragged will end up. 
   (transparent border to avoid a jumping effect when the border shows.) */
.concord-node > .concord-wrapper {
    border-bottom: 2px dotted transparent !important;
}
.concord-node.drop-sibling > .concord-wrapper {
    border-bottom: 2px dotted blue !important;
}
.concord-node > .concord-wrapper > .concord-text {
    border-bottom: 2px dotted transparent !important;
}
.concord-node.drop-child > .concord-wrapper > .concord-text {
    border-bottom: 2px dotted blue !important;
}