diff --git a/src/gl_helper/model.zig b/src/gl_helper/model.zig
index 01d8d98..1f53405 100644
--- a/src/gl_helper/model.zig
+++ b/src/gl_helper/model.zig
@@ -21,15 +21,16 @@ pub fn init(
     return .{ .data = data };
 }
 
-pub fn draw(self: *@This(), shader: Shader) void {
+pub fn draw(self: *@This(), allocator: std.mem.Allocator, shader: Shader) !void {
     var iter = self.data.depthFirstIterator();
-    while (iter.next()) |node| {
-        var rotation = node.val.rotation;
-        var current = node;
-        while (current.parent) |parent| {
-            rotation = zm.qmul(rotation, parent.val.rotation);
-            current = parent;
-        }
+    defer iter.deinit(allocator);
+    while (try iter.next(allocator)) |node| {
+        const rotation = node.val.rotation;
+        // var current = node;
+        // while (current.parent) |parent| {
+        //     rotation = zm.qmul(rotation, parent.val.rotation);
+        //     current = parent;
+        // }
 
         const model_matrix = zm.mul(zm.quatToMat(rotation), node.val.translation);
         const normal_matrix = zm.transpose(zm.inverse(model_matrix));
@@ -39,6 +40,6 @@ pub fn draw(self: *@This(), shader: Shader) void {
     }
 }
 
-pub fn deinit(self: *@This(), allocator: std.mem.Allocator) void {
-    self.data.deinit(allocator);
+pub fn deinit(self: *@This(), allocator: std.mem.Allocator) !void {
+    try self.data.deinit(allocator);
 }
diff --git a/src/main.zig b/src/main.zig
index 36c50fe..0fc4e36 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -97,7 +97,7 @@ pub fn main() !void {
     defer floor.delete();
 
     var robot = try initRobot(allocator, robot_texture);
-    defer robot.deinit(allocator);
+    defer robot.deinit(allocator) catch {};
 
     // uniform data
     var light_color = zm.f32x4(1, 1, 1, 1);
@@ -163,7 +163,7 @@ pub fn main() !void {
                 floor.draw(model_shader);
 
                 // animateRobot(&frame_counter, robot);
-                robot.draw(model_shader);
+                try robot.draw(allocator, model_shader);
             },
             .fish => {},
         }
diff --git a/src/tree.zig b/src/tree.zig
index 21a31f2..076468b 100644
--- a/src/tree.zig
+++ b/src/tree.zig
@@ -1,5 +1,6 @@
 const std = @import("std");
 const Allocator = std.mem.Allocator;
+const ArrayList = std.ArrayList;
 
 pub fn Tree(comptime T: type) type {
     return struct {
@@ -7,71 +8,90 @@ pub fn Tree(comptime T: type) type {
 
         root: Node,
 
-        const Children = std.ArrayList(Node);
+        const Children = ArrayList(Node);
         const Node = struct {
             val: T,
-            parent: ?*Node,
-            index: usize,
-            children: std.ArrayList(Node),
+            // index: usize,
+            children: ArrayList(Node),
 
-            pub fn init(val: T, parent: ?*Node, index: usize) Node {
+            pub fn init(val: T) Node {
                 return .{
                     .val = val,
                     .children = .empty,
-                    .parent = parent,
-                    .index = index,
                 };
             }
 
             pub fn append(self: *Node, allocator: Allocator, val: T) !void {
-                const child = Node.init(val, self, self.children.items.len);
+                const child = Node.init(val);
                 try self.children.append(allocator, child);
             }
         };
 
         pub fn init(val: T) @This() {
-            return .{ .root = .init(val, null, 0) };
+            return .{ .root = .init(val) };
         }
 
         pub const DepthFirstIterator = struct {
+            const Frame = struct {
+                parent: ?*Node,
+                index: usize,
+            };
             const State = enum {
                 GoDeeper,
                 GoBroader,
             };
             tree: *Tree(T),
             current: ?*Node,
+            path: ArrayList(Frame),
             state: State,
 
             pub fn init(tree: *Tree(T)) DepthFirstIterator {
                 return DepthFirstIterator{
                     .tree = tree,
                     .current = &tree.root,
+                    .path = .empty,
                     .state = State.GoDeeper,
                 };
             }
 
-            pub fn next(it: *DepthFirstIterator) ?*Node {
+            pub fn next(it: *DepthFirstIterator, allocator: Allocator) !?*Node {
                 // State machine
                 while (it.current) |current| {
                     switch (it.state) {
                         State.GoDeeper => {
                             // Follow child node until deepest possible level
                             if (current.children.items.len > 0) {
+                                try it.path.append(allocator, .{
+                                    .index = 0,
+                                    .parent = current,
+                                });
                                 it.current = &current.children.items[0];
                             } else {
                                 it.state = State.GoBroader;
+                                _ = it.path.pop();
                                 return current;
                             }
                         },
                         State.GoBroader => {
-                            if (current.parent) |parent| {
-                                if (parent.children.items.len - 1 > (current.index)) {
-                                    it.current = &parent.children.items[current.index + 1];
-                                    it.state = .GoDeeper;
+                            const last_frame = it.path.pop();
+                            if (last_frame) |frame| {
+                                if (frame.parent) |parent| {
+                                    if (parent.children.items.len > frame.index + 1) {
+                                        it.current = &parent.children.items[frame.index + 1];
+                                    } else {
+                                        it.current = parent;
+                                        // return it.path.pop().?.parent;
+                                    }
                                 } else {
-                                    it.current = current.parent;
-                                    return current.parent;
+                                    return null;
                                 }
+                                //     if (parent.children.items.len > current.index + 1) {
+                                //         it.current = &parent.children.items[current.index + 1];
+                                //         it.state = .GoDeeper;
+                                //     } else {
+                                //         it.current = current.parent;
+                                //         return current.parent;
+                                //     }
                             } else {
                                 return null;
                             }
@@ -84,15 +104,20 @@ pub fn Tree(comptime T: type) type {
             pub fn reset(it: *DepthFirstIterator) void {
                 it.current = it.tree.root;
             }
+
+            pub fn deinit(self: *DepthFirstIterator, allocator: Allocator) void {
+                self.path.deinit(allocator);
+            }
         };
 
         pub fn depthFirstIterator(tree: *@This()) DepthFirstIterator {
             return DepthFirstIterator.init(tree);
         }
 
-        pub fn deinit(self: *@This(), allocator: Allocator) void {
+        pub fn deinit(self: *@This(), allocator: Allocator) !void {
             var iterator = self.depthFirstIterator();
-            while (iterator.next()) |node| {
+            defer iterator.deinit(allocator);
+            while (try iterator.next(allocator)) |node| {
                 node.children.deinit(allocator);
             }
         }