diff --git a/src/dlib b/src/dlib
index b4bcfb7..c7f7752 160000
--- a/src/dlib
+++ b/src/dlib
@@ -1 +1 @@
-Subproject commit b4bcfb7929ca87d59a35719c43b34d64ecaec9a0
+Subproject commit c7f77523c4b7c86b625149ef7fde76257f6fcf51
diff --git a/src/editor/editor.d b/src/editor/editor.d
index fe02df6..4cf18ff 100644
--- a/src/editor/editor.d
+++ b/src/editor/editor.d
@@ -20,6 +20,7 @@ const u8[] FRAGMENT_BYTES = import("gui.frag.spv");
 
 const UI_COUNT = 5000;
 
+f32 g_delta = 0.0;
 Editor* g_editor;
 
 struct Editor
@@ -47,6 +48,8 @@ struct Editor
 	FontFace        font;
 	FontAtlasBuf    atlas_buf;
 
+	Stack!(UIPanel*) panel_stack;
+
 	UVec2 res;
 }
 
@@ -199,7 +202,7 @@ Cycle(Editor* ed, Inputs* inputs)
 	}
 
 	u32 prev_box_count = box_count;
-	f32 delta = DeltaTime(&timer);
+	g_delta = DeltaTime(&timer);
 	for(auto ev = inputs.list.first; ev != null; ev = ev.next)
 	{
 		count += 1;
@@ -218,106 +221,28 @@ Cycle(Editor* ed, Inputs* inputs)
 		}
 	}
 
-	static UIPanel* panel = null;
-	if (panel == null)
-	{
-		panel = Alloc!(UIPanel);
+	PanelStart("##Base", Vec3(0.5));
 
-		panel.split_axis = A2D.X;
-		panel.percent = 1.0;
-		panel.first = panel.last = Alloc!(UIPanel);
+	PanelStart("##horizontal1", Vec3(0.2, 0.3, 0.7));
 
-		panel.first.percent = 1.0;
+	PanelStart("##horizontal2", Vec3(0.2, 0.3, 0.7));
 
-		UIPanel* child = panel.first;
-		foreach(i; 0 .. 8)
-		{
-			UIPanel* p = Alloc!(UIPanel);
-
-			child.next = p;
-			panel.last = p;
-			child = p;
-		}
-	}
-
-	char[128] buf = 0;
+	char[128] buf;
 	f32 x_pct = 1.0/box_count;
-
-	if (box_count > prev_box_count)
-	{
-		u32 added = box_count - prev_box_count;
-		f32 insert_size = 0.0;
-		UIPanel* child = panel.first;
-		foreach(i; 0 .. prev_box_count)
-		{
-			child.anim.start = child.percent;
-			child.anim.end = x_pct;
-			child.anim.time_start = 0.2;
-			child.anim.time_remaining = 0.2;
-			
-			child = child.next;
-		}
-
-		foreach(i; 0 .. box_count-prev_box_count)
-		{
-			child.anim.start = insert_size;
-			child.anim.end = x_pct;
-			child.anim.time_start = 0.2;
-			child.anim.time_remaining = 0.2;
-			child.percent = insert_size;
-
-			child = child.next;
-		}
-	}
-	else if (box_count < prev_box_count)
-	{
-		UIPanel* child = panel.first;
-		foreach(i; 0 .. box_count)
-		{
-			child.anim.start = child.percent;
-			child.anim.end = x_pct;
-			child.anim.time_start = 0.2;
-			child.anim.time_remaining = 0.2;
-
-			child = child.next;
-		}
-	}
-	else
-	{
-		UIPanel* child = panel.first;
-		foreach(i; 0 .. box_count)
-		{
-			if (child.anim.time_remaining == 0.0) break;
-
-			f32 r = child.anim.time_remaining;
-
-			r -= delta;
-			if (r < 0.0)
-			{
-				r = 0.0;
-			}
-
-			f32 t = Remap(r, 0.0, child.anim.time_start, 1.0, 0.0);
-			child.percent = Mix(child.anim.start, child.anim.end, t);
-
-			child.anim.time_remaining = r;
-			if (r == 0.0)
-			{
-				child.anim.start = child.anim.end = child.anim.time_start = 0.0;
-			}
-
-			child = child.next;
-		}
-	}
-
-	UIPanel* child = panel.first;
 	foreach(i; 0 .. box_count)
 	{
 		buf.sformat("##%s", i);
-		DrawPanel(cast(u8[])buf, Vec4(Vec3(x_pct * i), 1.0), child);
-		child = child.next;
+		PanelStart(cast(u8[])buf, Vec3(x_pct * i));
+		PanelEnd();
 	}
 
+	PanelEnd();
+
+	PanelStart("##horizontal3", Vec3(0.2, 0.5, 0.9));
+	PanelEnd();
+
+	PanelEnd();
+
 	BeginFrame(&ed.rd);
 	
 	UVec2 ext = UVec2(GetExtent(&ed.rd));
diff --git a/src/editor/ui.d b/src/editor/ui.d
index db89413..e9b8a80 100644
--- a/src/editor/ui.d
+++ b/src/editor/ui.d
@@ -5,6 +5,7 @@ import dlib.alloc;
 import dlib.fonts;
 import vulkan;
 import widgets;
+import std.stdio;
 
 import editor;
 
@@ -30,13 +31,9 @@ struct UIContext
 	Rect                        padding;
 	u32                         tab_width;
 	f32                         text_scale;
-	Stack!(UIItem)              parent_stack;
+	UIItem*                     parent_stack;
 	Axis2D                      layout_axis;
-}
-
-struct Stack(T)
-{
-	T* first;
+	Vec2                        position;
 }
 
 struct UIBuffer
@@ -63,6 +60,7 @@ enum CtxProperty
 	TextScale,
 	TabWidth,
 	LayoutAxis,
+	Position,
 }
 
 alias CtxP = CtxProperty;
@@ -154,11 +152,15 @@ struct UIItem
 	UIItem*         prev;
 	UIItem*         parent;
 
+	UIItem*         list_next;
+	UIItem*         list_prev;
+
+	debug { u8[] debug_id; }
+
 	UISize[A2D.max] size;
 	Vec4[4]         bg_color;
 	Vec4[4]         border_color;
 	Rect            padding;
-	f32[A2D.max]    computed_rel_pos;
 	f32[A2D.max]    computed_size;
 	f32[A2D.max]    fixed_position;
 	Rect            rect;
@@ -194,10 +196,9 @@ UIBeginBuild()
 
 	ui.buffer.count = 0;
 
-	ClearStack(&g_ui_ctx.parent_stack, g_UI_NIL);
+	ClearParentStack();
 	
 	ui.root = RootItem();
-	PushParent(ui.root);
 }
 
 void
@@ -223,26 +224,25 @@ UIFinishBuild()
 	}
 
 	// 2. PercentOfParent (Upward dependant) size (pre-order) (Ignore downward dependant sizes)
-	u32 count = 0;
-	for(UIItem* item = ui.root; !Nil(item); item = Recurse!(UIR.PreOrder)(item, ui.root).next)
+	foreach(axis; A2D.min .. A2D.max)
 	{
-		for(UIItem* child = item.first; !Nil(child); child = child.next)
+		for(UIItem* item = ui.root; !Nil(item); item = Recurse!(UIR.PreOrder)(item, ui.root).next)
 		{
-			foreach(i, ref s; child.size)
+			for(UIItem* child = item.first; !Nil(child); child = child.next)
 			{
-				if (s.kind == SK.PercentOfParent)
+				if (child.size[axis].kind == SK.PercentOfParent)
 				{
 					UIItem* fixed_parent = g_UI_NIL;
 					for(UIItem* p = child.parent; !Nil(p); p = p.parent)
 					{
-						if (p.size[i].kind == SK.Pixels || p.size[i].kind == SK.TextContent)
+						if (p.size[axis].kind == SK.Pixels || p.size[axis].kind == SK.TextContent)
 						{
 							fixed_parent = p;
 							break;
 						}
 					}
 
-					child.computed_size[i] = fixed_parent.computed_size[i] * s.value;
+					child.computed_size[axis] = fixed_parent.computed_size[axis] * child.size[axis].value;
 				}
 			}
 		}
@@ -259,11 +259,33 @@ UIFinishBuild()
 				i32 pop_index = 0;
 				for(UIItem* i = item; !Nil(item) && pop_index <= rec.pop_count; i = i.parent, pop_index += 1)
 				{
+					if (i.size[axis].kind == SK.ChildrenSum)
+					{
+						f32 sum = 0.0;
+						for(UIItem* child = i.first; !Nil(child); child = child.next)
+						{
+							sum = axis == child.layout_axis ? sum + child.computed_size[axis] : Max(sum, child.computed_size[axis]);
+						}
+						i.computed_size[axis] = sum;
+					}
 				}
 			}
 		}
 	}
 	// 4. Solve violations e.g. extending past boundaries of parent (pre-order) 
+	foreach(axis; A2D.min .. A2D.max)
+	{
+		for(UIItem* item = ui.root; !Nil(item); item = Recurse!(UIR.PreOrder)(item, ui.root).next)
+		{
+			if (!Nil(item.parent))
+			{
+				if (item.parent.computed_size[axis] < item.computed_size[axis])
+				{
+					item.computed_size[axis] = item.parent.computed_size[axis];
+				}
+			}
+		}
+	}
 
 	// 5. Compute relative positions of each widgets (pre-order)
 	foreach(axis; A2D.min .. A2D.max)
@@ -271,12 +293,12 @@ UIFinishBuild()
 		for(UIItem* item = ui.root; !Nil(item); item = Recurse!(UIR.PreOrder)(item, ui.root).next)
 		{
 			f32 layout_position = 0.0;
-
 			for(UIItem* child = item.first; !Nil(child); child = child.next)
 			{
-				child.computed_rel_pos[axis] = layout_position;
-				child.rect.vec0.v[axis] = layout_position;
-				child.rect.vec1.v[axis] = layout_position + child.computed_size[axis];
+				child.fixed_position[axis] = layout_position;
+
+				child.rect.vec0.v[axis] = item.rect.vec0.v[axis] + child.fixed_position[axis];
+				child.rect.vec1.v[axis] = child.rect.vec0.v[axis] + child.computed_size[axis];
 
 				if (axis == item.layout_axis)
 				{
@@ -286,19 +308,46 @@ UIFinishBuild()
 		}
 	}
 
+	u32 count = 0;
 	for(UIItem* item = ui.root; !Nil(item); item = Recurse!(UIR.PreOrder)(item, ui.root).next)
 	{
-		for(UIItem* child = item.first; !Nil(child); child = child.next)
+		if (item.flags & UIP.DrawBackground)
 		{
-			if (!Nil(child))
-			{
-				if (child.flags & UIP.DrawBackground)
-				{
-					DrawRect(ui, child);
-				}
-			}
+			DrawRect(ui, item);
 		}
 	}
+
+	WidgetsComplete();
+}
+
+void
+PrintTree(UIItem* item, u32 count = 0, string prefix = "", bool is_left = false)
+{
+	if (!Nil(item))
+	{
+		writeln(is_left ? "f" : "l", count, prefix, is_left ? "├──" : "└──", item.debug_id);
+
+		prefix ~= is_left ? "│   " : "    ";
+		PrintTree(item.first, count + 1, prefix, true);
+		PrintTree(item.next, count + 1, prefix, false);
+	}
+}
+
+void
+PushParent(UIItem* parent)
+{
+	auto ctx = GetCtx();
+	parent.list_next = ctx.parent_stack;
+	ctx.parent_stack = parent;
+}
+
+UIItem*
+PopParent()
+{
+	auto ctx = GetCtx();
+	UIItem* parent = ctx.parent_stack;
+	ctx.parent_stack = parent.list_next;
+	return parent;
 }
 
 UIItem*
@@ -307,8 +356,8 @@ BuildItem(UIKey key, UIProperties flags)
 	UIContext* ui = GetCtx();
 
 	UIItem* item = Get(key);
-	item.first = item.last = item.next = item.prev = item.parent = g_UI_NIL;
-	item.computed_rel_pos = item.computed_size = 0;
+	item.first = item.last = item.next = item.prev = item.parent = item.list_next = item.list_prev = g_UI_NIL;
+	item.computed_size = 0;
 
 	item.flags = flags;
 	item.size = ui.size_axes;
@@ -328,31 +377,25 @@ BuildItem(UIKey key, UIProperties flags)
 		item.text_scale = ui.text_scale;
 	}
 
-	item.parent = ui.parent_stack.first;
+	item.parent = ui.parent_stack;
 	if (!Nil(item.parent))
 	{
 		DLLPush(item.parent, item, g_UI_NIL);
 	}
 
+	debug
+	{
+		item.debug_id = key.text;
+	}
+
 	return item;
 }
 
 void
-ClearStack(T)(Stack!(T)* stack, T* nil)
+ClearParentStack()
 {
-	while(SPop(stack, nil) != nil) {}
-}
-
-void
-PushParent(UIItem* parent)
-{
-	SPush(&g_ui_ctx.parent_stack, parent, g_UI_NIL);
-}
-
-UIItem*
-PopParent()
-{
-	return SPop(&g_ui_ctx.parent_stack, g_UI_NIL);
+	auto ctx = GetCtx();
+	ctx.parent_stack = g_UI_NIL;
 }
 
 void
@@ -378,7 +421,8 @@ InitUIContext(Renderer* rd)
 	g_ui_ctx.buffer.mapped_idx = idx;
 	g_ui_ctx.buffer.vtx = vtx.data;
 	g_ui_ctx.buffer.idx = idx.data;
-	g_ui_ctx.parent_stack.first = g_UI_NIL;
+
+	InitWidgetContext();
 }
 
 UIKey
@@ -551,17 +595,23 @@ Recurse(alias mode)(UIItem* item, UIItem* root)
 	UIItem* sibling, child;
 	UIItemRec result = UIItemRec(next: g_UI_NIL);
 
-	static if (mode == UIR.PostOrder) sibling = item.next; else sibling = item.prev;
-	static if (mode == UIR.PostOrder) child   = item.prev; else child   = item.last;
+	static if (mode == UIR.PostOrder) child   = item.last; else child   = item.first;
 
 	if (!Nil(child))
 	{
 		result.next = child;
 		result.push_count = 1;
 	}
-	else for(UIItem* i = sibling; !Nil(i) && i != root; i = i.parent)
+	else for(UIItem* i = item; !Nil(i) && i != root; i = i.parent)
 	{
-		static if (mode == UIR.PostOrder) sibling = i.next; else sibling = i.prev;
+		static if (mode == UIR.PostOrder)
+		{
+			sibling = i.prev;
+		}
+		else
+		{
+			sibling = i.next;
+		}
 
 		if (!Nil(sibling))
 		{
@@ -584,6 +634,11 @@ SetProp(alias P, T)(T value)
 		static if (P == CtxP.LayoutAxis) g_ui_ctx.layout_axis = value;
 		else static assert(false, "Unknown property for type Axis2D");
 	}
+	else static if (is(T: Vec2))
+	{
+		static if (P == CtxP.Position) g_ui_ctx.position = value;
+		else static assert(false, "Unknown property for type Vec2");
+	}
 	else static if (is(T: Vec4))
 	{
 		static if      (P == CtxP.BGColor)     g_ui_ctx.bg_cols     = [value, value, value, value];
diff --git a/src/editor/widgets.d b/src/editor/widgets.d
index e5ea738..af8ad50 100644
--- a/src/editor/widgets.d
+++ b/src/editor/widgets.d
@@ -1,5 +1,6 @@
 import dlib;
 
+import editor;
 import ui;
 
 struct WidgetAnimation
@@ -10,6 +11,18 @@ struct WidgetAnimation
 	f32 time_remaining;
 }
 
+WidgetContext g_widget_ctx;
+const UIPanel g_ui_panel;
+UIPanel* g_PANEL_NIL;
+
+struct WidgetContext
+{
+	u64                          frame;
+	Arena                        arena;
+	HashTable!(UIHash, UIPanel*) panels;
+	UIPanel*                     parent_panel;
+}
+
 struct UIPanel
 {
 	Axis2D split_axis;
@@ -17,12 +30,41 @@ struct UIPanel
 
 	UIPanel* first;
 	UIPanel* last;
+	UIPanel* prev;
 	UIPanel* next;
-	u32      count;
+	UIPanel* parent;
+
+	UIPanel* list_next;
+
+	u64      last_frame;
+	bool     new_children;
+	u32      child_count;
 
 	WidgetAnimation anim;
 }
 
+void
+InitWidgetContext()
+{
+	g_PANEL_NIL = cast(UIPanel*)&g_ui_panel;
+
+	g_widget_ctx.arena = CreateArena(MB(1));
+	g_widget_ctx.parent_panel = g_PANEL_NIL;
+	g_widget_ctx.panels = CreateHashTable!(UIHash, UIPanel*)(6);
+}
+
+void
+WidgetsComplete()
+{
+	g_widget_ctx.frame += 1;
+}
+
+bool
+Nil(UIPanel* panel)
+{
+	return panel == g_PANEL_NIL || panel == null;
+}
+
 UIItem*
 RootItem()
 {
@@ -37,22 +79,141 @@ RootItem()
 	
 	UIItem* item = BuildItem(key, UIP.DrawBackground);
 
+	UIContext* ui = GetCtx();
+
+	PushParent(ui.root);
+
+	assert(g_widget_ctx.parent_panel == g_PANEL_NIL);
+
 	return item;
 }
 
 UIItem*
-DrawPanel(u8[] str, Vec4 col, UIPanel* panel)
+PanelStart(string str, Vec3 col)
+{
+	u8[] u8_str = (cast(u8*)str.ptr)[0 .. str.length];
+	return PanelStart(u8_str, col);
+}
+
+UIPanel*
+GetPanel(UIKey key)
+{
+	UIPanel* panel;
+	Result!(UIPanel*) result = g_widget_ctx.panels[key.hash];
+	if (result.ok)
+	{
+		panel = result.value;
+	}
+	else
+	{
+		panel = Alloc!(UIPanel)(&g_widget_ctx.arena);
+		panel.last_frame = u64.max;
+		g_widget_ctx.panels[key.hash] = panel;
+	}
+
+	return panel;
+}
+
+UIItem*
+PanelStart(u8[] str, Vec3 col)
 {
 	UIKey key = MakeKey(str);
+	UIPanel* panel = GetPanel(key);
 
-	f32 x_pct = panel.split_axis == A2D.X ? panel.percent : 1.0;
-	f32 y_pct = panel.split_axis == A2D.Y ? panel.percent : 1.0;
+	panel.first = panel.last = panel.next = panel.list_next = g_PANEL_NIL;
+	panel.child_count = 0;
 
-	SetProp!(CtxP.AxisX)(UISize(SK.PercentOfParent, x_pct));
-	SetProp!(CtxP.AxisY)(UISize(SK.PercentOfParent, y_pct));
-	SetProp!(CtxP.BGColor)(col);
+	if (panel.anim.time_remaining > 0.0)
+	{
+		f32 r = panel.anim.time_remaining;
+
+		r -= g_delta;
+		if (r < 0.0)
+		{
+			r = 0.0;
+		}
+		Logf("%f", r);
+
+		f32 t = Remap(r, 0.0, panel.anim.time_start, 1.0, 0.0);
+		panel.percent = Lerp(panel.anim.start, panel.anim.end, t);
+
+		panel.anim.time_remaining = r;
+		if (r == 0.0)
+		{
+			panel.anim.start = panel.anim.end = panel.anim.time_start = 0.0;
+		}
+	}
+
+	panel.parent = g_widget_ctx.parent_panel;
+	panel.list_next = g_widget_ctx.parent_panel;
+	g_widget_ctx.parent_panel = panel;
+
+	f32 x_pct = 1.0, y_pct = 1.0;
+	if (!Nil(panel.parent))
+	{
+		if (panel.parent.split_axis == A2D.X)
+		{
+			x_pct = panel.percent;
+		}
+		else
+		{
+			y_pct = panel.percent;
+		}
+
+		if (panel.last_frame != g_widget_ctx.frame)
+		{
+			Logf("new");
+			panel.parent.new_children = true;
+			panel.anim.start = panel.anim.end = panel.anim.time_start = panel.anim.time_remaining = 0.0;
+		}
+
+		panel.child_count += 1;
+		DLLPush(panel.parent, panel, g_PANEL_NIL);
+	}
+
+	SetProp!(CtxP.LayoutAxis)(panel.split_axis);
+	SetProp!(CtxP.AxisX)(UISize(SK.PercentOfParent, x_pct, 1.0));
+	SetProp!(CtxP.AxisY)(UISize(SK.PercentOfParent, y_pct, 1.0));
+	SetProp!(CtxP.BGColor)(Vec4(col, 1.0));
 
 	UIItem* item = BuildItem(key, UIP.DrawBackground);
 
+	PushParent(item);
+
+	panel.last_frame = g_widget_ctx.frame + 1;
+
 	return item;
 }
+
+void
+PanelEnd()
+{
+	UIPanel* parent = g_widget_ctx.parent_panel;
+	if (parent.new_children)
+	{
+		f32 new_percent = 1.0/cast(f32)(parent.child_count);
+		for(UIPanel* child = parent.first; !Nil(child); child = child.next)
+		{
+			f32 percent = child.percent;
+			if (percent > 0.0)
+			{
+				percent -= new_percent/cast(f32)(parent.child_count-1);
+			}
+			else
+			{
+				percent = new_percent;
+			}
+
+			child.anim.start = child.percent;
+			child.anim.end = new_percent;
+			child.anim.time_start = 0.2;
+			child.anim.time_remaining = 0.2;
+			child.percent = percent;
+		}
+
+		parent.new_children = false;
+	}
+
+	g_widget_ctx.parent_panel = g_widget_ctx.parent_panel.list_next;
+	PopParent();
+}