diff --git a/OZprivate/rawJS/OZTreeModule/src/controller/controller_anim.js b/OZprivate/rawJS/OZTreeModule/src/controller/controller_anim.js
index 0606f652b..4cdba567c 100755
--- a/OZprivate/rawJS/OZTreeModule/src/controller/controller_anim.js
+++ b/OZprivate/rawJS/OZTreeModule/src/controller/controller_anim.js
@@ -184,8 +184,7 @@ export default function (Controller) {
         let anchor_node = this.dynamic_load_and_calc(dest_OZid, {
           generation_at_searched_node: config.generation_at_searched_node
         });
-        position_helper.deanchor(this.root);
-        position_helper.reanchor_at_node(anchor_node);
+        position_helper.reanchor_at_node(anchor_node, this.root);
         this.re_calc();
         this.trigger_refresh_loop();
         resolve()
diff --git a/OZprivate/rawJS/OZTreeModule/src/factory/midnode.js b/OZprivate/rawJS/OZTreeModule/src/factory/midnode.js
index e3c3acfcd..dd8025db4 100755
--- a/OZprivate/rawJS/OZTreeModule/src/factory/midnode.js
+++ b/OZprivate/rawJS/OZTreeModule/src/factory/midnode.js
@@ -43,9 +43,9 @@ class Midnode {
     this.arcr = 1.0;
     this.arcx = 1.0;
     this.arcy = 1.0;
-    this.nextr = new Array(config.factory.child_num);
-    this.nextx = new Array(config.factory.child_num);
-    this.nexty = new Array(config.factory.child_num);
+    this.nextr = new Array(config.factory.child_num);  // Relative radius/scale to assign to children, as decided by view _pre_calc() functions
+    this.nextx = new Array(config.factory.child_num);  // Relative x-location ...
+    this.nexty = new Array(config.factory.child_num);  // Relative y-location ...
     this.gxmin = 1.0;  // Node bounding box
     this.gymin = 1.0;  // Node bounding box
     this.hxmin = 1.0;  // Node-and-descendants bounding box
@@ -55,13 +55,13 @@ class Midnode {
     this.hxmax = 1.0;  // Node-and-descendants bounding box
     this.hymax = 1.0;  // Node-and-descendants bounding box
     
-    this.xvar = 1.0;
-    this.yvar = 1.0;
-    this.rvar = 1.0;
+    this.xvar = 1.0;  // x-location of node relative to graphref node updated by position_helper:drawreg_target()
+    this.yvar = 1.0;  // y-location of node ...
+    this.rvar = 1.0;  // radius/scale of node ...
     this.gvar = false;  // gvar is true if this node itself needs to be drawn on screen (i.e onezoom.config.debug_bounding_box = 1)
     this.dvar = false;  // dvar is true if this node (or a descendent node) needs to be drawn on the screen (i.e onezoom.config.debug_bounding_box = 4)
-    this.graphref = false;
-    this.targeted = false;
+    this.graphref = false;  // true if this node (or a descendent node) is the "referencing node", i.e. the node from which xvar/yvar/rvar are relative to
+    this.targeted = false;  // true if this node (or a descendent node) is the destination for the current flight
     
     this.child_leaf_meta_start = new Array(config.factory.child_num);
     this.child_leaf_meta_end = new Array(config.factory.child_num);
@@ -291,7 +291,20 @@ class Midnode {
     this._picID_credit = null;
     this._detail_fetched = false;
   }
-  
+
+  /**
+   * Text representation of node, for debugging purposes
+   *
+   * Use with console log, e.g: console.log("Reanchoring to " + node);
+   * (NB "+", not ",")
+   */
+  toString() {
+    return [
+      this.cname || this.latin_name || 'Node',
+      this.ott ? '@=' + this.ott : '@_ozid=' + this.ozid,
+    ].join(" ");
+  }
+
   /**
    * Returns the OZid
    * i.e. negative metacode for leaf, positive metacode for interior node
diff --git a/OZprivate/rawJS/OZTreeModule/src/position_helper.js b/OZprivate/rawJS/OZTreeModule/src/position_helper.js
index f01f40eaf..bd77a234e 100755
--- a/OZprivate/rawJS/OZTreeModule/src/position_helper.js
+++ b/OZprivate/rawJS/OZTreeModule/src/position_helper.js
@@ -132,6 +132,9 @@ function get_xyr_target(node, x2,y2,r2,into_node) {
   }
 }
 
+/**
+ *  Walk tree from (node), probably root, turning graphref off
+ */
 function deanchor(node) {
   if (node.graphref) {
     let length = node.children.length;
@@ -370,36 +373,52 @@ function pan_zoom(prop_p, prop_z) {
   tree_state.yp = tree_centreY + y_add2*(1-prop_p) + (pre_yp2-y_add2-tree_centreY) * Math.pow(r_mult2,prop_z);
 }
 
-function reanchor_at_node(node) {
-  node.graphref = true;
-  if (node.upnode) {
-    reanchor_at_node(node.upnode);
+/**
+ * Force the anchor to be the given (node),
+ * (i.e. set graphref on node and all it's ancestors)
+ */
+function reanchor_at_node(node, root_node) {
+  // Set graphref false everywhere
+  deanchor(root_node);
+
+  // Walk up tree from (node), setting graphref
+  while (node.upnode) {
+    node.graphref = true;
+    node = node.upnode;
   }
+  // Set graphref on root node
+  node.graphref = true;
 }
 
+/**
+ * Walk tree, anchoring to the first node on-screen that has 2.2 < node.rvar < 22000
+ * (i.e. set graphref on this node and it's ancestors)
+ */
 function reanchor(node) {
-  if (node.dvar) {
-    node.graphref = true;
-    if (node.gvar || !node.has_child || (node.rvar > 2.2 && node.rvar < 22000)) {
-      tree_state.xp = node.xvar;
-      tree_state.yp = node.yvar;
-      tree_state.ws = node.rvar / 220;
-      let length = node.children.length; 
-      for (let i=0; i<length; i++) {
-        deanchor(node.children[i]);
-      }
-    } else {
-      let length = node.children.length;
-      for (let i=0; i<length; i++) {
-        if (node.children[i].dvar) {
-          reanchor(node.children[i]);
-          for (let j=0; j<length; j++) {
-            if (i !== j) {
-              deanchor(node.children[j]);
-            }
+  // If this node (or it's desendents) aren't visible, don't bother
+  if (!node.dvar) return;
+
+  node.graphref = true;
+  if (node.gvar || !node.has_child || (node.rvar > 2.2 && node.rvar < 22000)) {
+    // Anchor to this node
+    tree_state.xp = node.xvar;
+    tree_state.yp = node.yvar;
+    tree_state.ws = node.rvar / 220;
+    // Deanchor everything below this node
+    for (let i=0; i<node.children.length; i++) {
+      deanchor(node.children[i]);
+    }
+  } else {
+    // Recurse, anchoring to the first visible child
+    for (let i=0; i<node.children.length; i++) {
+      if (node.children[i].dvar) {
+        reanchor(node.children[i]);
+        for (let j=0; j<node.children.length; j++) {
+          if (i !== j) {
+            deanchor(node.children[j]);
           }
-          break;
         }
+        break;
       }
     }
   }
@@ -416,4 +435,4 @@ function set_anim_speed(val) {
   global_anim_speed = val;
 }
 
-export {deanchor, reanchor, reanchor_at_node, target_by_code, clear_target, perform_actual_fly, get_anim_speed, set_anim_speed};
+export {reanchor, reanchor_at_node, target_by_code, clear_target, perform_actual_fly, get_anim_speed, set_anim_speed};
diff --git a/OZprivate/rawJS/OZTreeModule/src/projection/re_calc.js b/OZprivate/rawJS/OZTreeModule/src/projection/re_calc.js
index 80eac6368..dc15de201 100755
--- a/OZprivate/rawJS/OZTreeModule/src/projection/re_calc.js
+++ b/OZprivate/rawJS/OZTreeModule/src/projection/re_calc.js
@@ -32,7 +32,7 @@ function drawreg(node, x, y, r) {
         }
       }
       
-      if(node_descendants_in_screen(node)) {
+      if(node_on_screen(node, true)) {
         if (node.rvar > tree_state.threshold) {
           for (let other=0; other<length; other++) {
             if (other !== index) {
@@ -66,7 +66,7 @@ function drawreg2(node, x, y, r) {
   node.rvar = r;
   node.dvar = false;	
   node.gvar = false;
-  if(node_descendants_in_screen(node)) {
+  if(node_on_screen(node, true)) {
     if (node.has_child) {
       if (r > tree_state.threshold) {
         let length = node.children.length;
@@ -101,26 +101,24 @@ function get_dvar_by_children(node) {
   return dvar;
 }
 
-/** Does the given node and it's descendants fit on screen? */
-function node_descendants_in_screen(node) {
-  if ((node.xvar + node.rvar * node.hxmax) < 0) return false;
-  else if ((node.xvar + node.rvar * node.hxmin) > tree_state.widthres) return false;
-  else if ((node.yvar + node.rvar * node.hymax) < 0) return false;
-  else if ((node.yvar + node.rvar * node.hymin) > tree_state.heightres) return false;
-  else return true;
-}
+/**
+ * Does the bounding box of the node / node-and-descendants fit on screen?
+ */
+function node_on_screen(node, inclDescendants) {
+  const x1 = node.xvar + node.rvar * (inclDescendants ? node.hxmin : node.gxmin);
+  const x2 = node.xvar + node.rvar * (inclDescendants ? node.hxmax : node.gxmax);
+  const y1 = node.yvar + node.rvar * (inclDescendants ? node.hymin : node.gymin);
+  const y2 = node.yvar + node.rvar * (inclDescendants ? node.hymax : node.gymax);
 
-/** Does the given node fit on screen? */
-function node_in_screen(node) {
-  if ((node.xvar + node.rvar * node.gxmax) < 0) return false;
-  else if ((node.xvar + node.rvar * node.gxmin) > tree_state.widthres) return false;
-  else if ((node.yvar + node.rvar * node.gymax) < 0) return false;
-  else if ((node.yvar + node.rvar * node.gymin) > tree_state.heightres) return false;
-  else return true;
+  if (x2 < 0) return false;
+  if (x1 > tree_state.widthres) return false;
+  if (y2 < 0) return false;
+  if (y1 > tree_state.heightres) return false;
+  return true;
 }
 
 function set_node_gvar_dvar(node) {
-  if(node_in_screen(node)) {
+  if(node_on_screen(node, false)) {
     node.gvar = true;        
     node.dvar = true;        
   } else {
diff --git a/OZprivate/rawJS/OZTreeModule/src/projection/shape_manager.js b/OZprivate/rawJS/OZTreeModule/src/projection/shape_manager.js
index cafe08d41..197e41182 100755
--- a/OZprivate/rawJS/OZTreeModule/src/projection/shape_manager.js
+++ b/OZprivate/rawJS/OZTreeModule/src/projection/shape_manager.js
@@ -64,8 +64,23 @@ function draw_bounding_box(node, shapes) {
   }
 
   if (debug & 0x2) { // Bounding box for node + parent
+    s = BezierShape.create();
+    s.sx = s.sy = s.ex = s.ey = null;
+    s.path_points.push(['move', node.xvar + node.rvar * node.gxmin, node.yvar + node.rvar * node.gymin]);
+    s.path_points.push(['line', node.xvar + node.rvar * node.gxmin, node.yvar + node.rvar * node.gymax]);
+    s.path_points.push(['line', node.xvar + node.rvar * node.gxmax, node.yvar + node.rvar * node.gymax]);
+    s.path_points.push(['line', node.xvar + node.rvar * node.gxmax, node.yvar + node.rvar * node.gymin]);
+    s.path_points.push(['line', node.xvar + node.rvar * node.gxmin, node.yvar + node.rvar * node.gymin]);
+    s.do_stroke = true;
+    s.stroke.line_width = 1;
+    s.height = 0;
+    s.stroke.color = 'hsl(' + Math.sin(node.metacode) * 360 + ', 100%, 80%)';
+    shapes.push(s);
+  }
+
+  if (debug & 0x1) { // Bounding box text label
     s = TextShape.create();
-    s.text = "" + node.latin_name;
+    s.text = "" + node.toString();
     s.width = (node.xvar + node.rvar * node.gxmax) - (node.xvar + node.rvar * node.gxmin);
     s.height = 5;
     s.x = node.xvar + node.rvar * node.gxmin + (s.width / 2);
@@ -79,20 +94,6 @@ function draw_bounding_box(node, shapes) {
     shapes.push(s);
   }
 
-  if (debug & 0x1) { // Bounding box text label
-    s = BezierShape.create();
-    s.sx = s.sy = s.ex = s.ey = null;
-    s.path_points.push(['move', node.xvar + node.rvar * node.gxmin, node.yvar + node.rvar * node.gymin]);
-    s.path_points.push(['line', node.xvar + node.rvar * node.gxmin, node.yvar + node.rvar * node.gymax]);
-    s.path_points.push(['line', node.xvar + node.rvar * node.gxmax, node.yvar + node.rvar * node.gymax]);
-    s.path_points.push(['line', node.xvar + node.rvar * node.gxmax, node.yvar + node.rvar * node.gymin]);
-    s.path_points.push(['line', node.xvar + node.rvar * node.gxmin, node.yvar + node.rvar * node.gymin]);
-    s.do_stroke = true;
-    s.stroke.line_width = 1;
-    s.height = 0;
-    s.stroke.color = 'hsl(' + Math.sin(node.metacode) * 360 + ', 100%, 80%)';
-    shapes.push(s);
-  }
 }
 
 function height_comparator(a, b) {