diff --git a/gui/gui.c b/gui/gui.c
index 55fc719..d7a92ee 100644
--- a/gui/gui.c
+++ b/gui/gui.c
@@ -188,6 +188,9 @@ struct GUI_Subtree {
 	GUI_Subtree *next;
 	GUI_Subtree *structural_parent;
 
+	// TODO(Zelaven):
+	// GUI_Rectangle cliprect;
+
 	GUI_Node_Reference relative_to;
 	int flat_offset_x;
 	int flat_offset_y;
@@ -195,20 +198,30 @@ struct GUI_Subtree {
 	int offset_relative_node_percentage_y;
 	int offset_own_size_percentage_x;
 	int offset_own_size_percentage_y;
+};
+
+
+typedef struct {
+	GUI_Subtree *first_subtree;
+	//GUI_Subtree *last_subtree;
+	//GUI_Subtree *current_subtree;
 
 	GUI_Draw_Command *first_draw_command;
 	int num_draw_commands;
-	Pixel_Buffer *pixel_buffer;
-};
+	Pixel_Buffer pixel_buffer;
+} GUI_Layer;
 
 
 typedef struct {
 	//RDIC_Context rdic;
 
-	GUI_Subtree *first_subtree;
-	GUI_Subtree *last_subtree;
+	//GUI_Subtree *first_subtree;
+	//GUI_Subtree *last_subtree;
 	GUI_Subtree *current_subtree;
 
+	GUI_Layer background_layer;
+	GUI_Layer top_layer;
+
 	GUI_Node_Reference focused_node;
 	GUI_Node_Reference hovered_node;
 	GUI_Node_Reference top_node_under_cursor;
@@ -316,8 +329,25 @@ void gui_apply_input(
 	int mouse_x,
 	int mouse_y)
 {
+	// --- Mouse Input ---
+	// NOTE(Zelaven): First hit test against layers.
+	GUI_Layer *hit_layer = &context->background_layer;
+	{
+		GUI_Layer *top_layer = &context->top_layer;
+		if(top_layer->first_subtree != NULL)
+		{
+			GUI_Node *top_layer_root =
+				(GUI_Node*)top_layer->first_subtree->rdic.root;
+			if(point_in_rect(mouse_x, mouse_y, top_layer_root->rect))
+			{
+				hit_layer = &context->top_layer;
+			}
+		}
+	}
+
 	//GUI_Node *top_node_under_cursor = (GUI_Node*)context->rdic.root;
-	GUI_Node *top_node_under_cursor = (GUI_Node*)context->first_subtree->rdic.root;
+	//GUI_Node *top_node_under_cursor = (GUI_Node*)context->first_subtree->rdic.root;
+	GUI_Node *top_node_under_cursor = (GUI_Node*)hit_layer->first_subtree->rdic.root;
 	GUI_Node *current_node = (GUI_Node*)top_node_under_cursor->rdic_node.first_child;
 	int mouse_over_node = 0;
 	while(current_node != NULL)
@@ -410,8 +440,8 @@ GUI_Node_Reference gui_context_start_frame(
 
 	static GUI_Subtree background_subtree = {0};
 	background_subtree.rdic.node_freelist = context->node_freelist;
-	context->first_subtree = &background_subtree;
-	context->last_subtree = &background_subtree;
+	context->background_layer.first_subtree = &background_subtree;
+	//context->background_layer.last_subtree = &background_subtree;
 	context->current_subtree = &background_subtree;
 
 	GUI_Node_Reference new_root_reference = {
@@ -445,8 +475,9 @@ GUI_Node_Reference gui_context_start_frame(
 void gui_context_finish_frame(
 	GUI_Context *context)
 {
-	rdic_context_finish_frame(&context->first_subtree->rdic);
-	context->node_freelist = context->first_subtree->rdic.node_freelist;
+	rdic_context_finish_frame(&context->background_layer.first_subtree->rdic);
+	context->node_freelist =
+		context->background_layer.first_subtree->rdic.node_freelist;
 }
 
 GUI_Node_Reference gui_push_subtree(
@@ -461,9 +492,10 @@ GUI_Node_Reference gui_push_subtree(
 	context->node_freelist = context->current_subtree->rdic.node_freelist;
 	subtree->rdic.node_freelist = context->node_freelist;
 
-	context->last_subtree->next = subtree;
-	subtree->prev = context->last_subtree;
-	context->last_subtree = subtree;
+	// NOTE(Zelaven): Well, not being able to do this is a problem...
+	//context->last_subtree->next = subtree;
+	//subtree->prev = context->last_subtree;
+	//context->last_subtree = subtree;
 
 	subtree->structural_parent = context->current_subtree;
 	context->current_subtree = subtree;
@@ -3158,7 +3190,7 @@ int main(void)
 			//gui_layout_nodes(&context);
 			#if 1
 			for(
-				GUI_Subtree *current = context.first_subtree;
+				GUI_Subtree *current = context.background_layer.first_subtree;
 				current != NULL;
 				current = current->next)
 			{