diff --git a/otg/core/src/types.rs b/otg/core/src/types.rs
index 7ce672b..c89b55c 100644
--- a/otg/core/src/types.rs
+++ b/otg/core/src/types.rs
@@ -4,7 +4,7 @@ use config_derive::ConfigOption;
 use serde::{Deserialize, Serialize};
 use sgf::GameTree;
 use std::{
-    cell::RefCell, collections::{HashMap, VecDeque}, fmt, ops::Deref, path::PathBuf, time::Duration
+    collections::{HashMap, VecDeque}, fmt, ops::Deref, path::PathBuf, time::Duration
 };
 use thiserror::Error;
 
@@ -254,9 +254,15 @@ impl Deref for DepthTree {
 
 #[derive(Debug)]
 pub struct SizeNode {
-    node_id: nary_tree::NodeId,
-    parent: Option<nary_tree::NodeId>,
+    /// Use this to map back to the node in the original game tree. This way we know how to
+    /// correspond from a node in the review tree back to there.
+    #[allow(dead_code)]
+    game_node_id: nary_tree::NodeId,
+
+    /// How deep into the tree is this node?
     depth: usize,
+
+    /// How far from the leftmost margin is this node?
     width: usize,
 }
 
@@ -398,7 +404,7 @@ impl DepthTree {
     pub fn bfs_iter(&self) -> BFSIter<'_, SizeNode> {
         let mut queue = VecDeque::new();
         queue.push_back(self.0.root().unwrap());
-        BFSIter { tree: self, queue }
+        BFSIter { queue }
     }
 }
 
@@ -425,8 +431,7 @@ impl<'a> From<&'a GameTree> for DepthTree {
                                               // this branch.
 
                 let dest_root_id = tree.set_root(SizeNode {
-                    node_id: source_root_node.node_id(),
-                    parent: None,
+                    game_node_id: source_root_node.node_id(),
                     depth: 0,
                     width: 0,
                 });
@@ -441,8 +446,7 @@ impl<'a> From<&'a GameTree> for DepthTree {
                     let mut dest_parent = tree.get_mut(*dest_parent_id).unwrap();
 
                     let new_depth_node = SizeNode {
-                        node_id: source_node.node_id(),
-                        parent: Some(*dest_parent_id),
+                        game_node_id: source_node.node_id(),
                         depth: 1 + dest_parent.data().depth,
                         width: dest_parent.data().width,
                     };
@@ -521,7 +525,6 @@ impl<'a> From<&'a GameNode> for Tree<Uuid> {
 */
 
 pub struct BFSIter<'a, T> {
-    tree: &'a DepthTree,
     queue: VecDeque<nary_tree::NodeRef<'a, T>>,
 }