diff --git a/example/main.odin b/example/main.odin
index 97de745..d39f9ba 100644
--- a/example/main.odin
+++ b/example/main.odin
@@ -13,6 +13,30 @@ INPUT_FLOAT_CHARACTERS :: 32
 
 v2 :: [2]f32
 V2_ONE :: v2{1.0, 1.0}
+V2_LEFT :: v2{-1.0, 0.0}
+V2_RIGHT :: v2{1.0, 0.0}
+V2_UP :: v2{-1.0, 0.0}
+V2_DOWN :: v2{1.0, 0.0}
+
+UiContainerType :: enum {
+	Normal,
+	Matrix,
+}
+
+UiElementData_Container :: struct {
+	type: UiContainerType,
+	thickness: f32,
+}
+
+UiElementData_Slider :: struct {
+	min, max: f32,
+	value:    ^f32,
+}
+
+UiElementData_FloatInput :: struct {
+	value: ^f32,
+	value_string: cstring,
+}
 
 main :: proc() {
 	rl.SetTraceLogLevel(.WARNING)
@@ -46,7 +70,9 @@ main :: proc() {
 			ui.container_end()
 		}
 
-		ui.container_begin(dimensions = {ui.SIZE_AUTO, ui.Size_Percentage(0.2)}, config = inner_container_config)
+		container_data := new(UiElementData_Container, context.temp_allocator)
+		container_data^ = {type = .Matrix, thickness = 2.0}
+		ui.container_begin(dimensions = {ui.SIZE_AUTO, ui.Size_Percentage(0.2)}, config = inner_container_config, data = container_data)
 		for j in 0..<10 {
 			config := button_config
 			config.label = fmt.ctprintf("%d", 70 + j)
@@ -99,25 +125,15 @@ main :: proc() {
 	}
 }
 
-ElementData_Slider :: struct {
-	min, max: f32,
-	value:    ^f32,
-}
-
-ElementData_FloatInput :: struct {
-	value: ^f32,
-	value_string: cstring,
-}
-
 ui_slider_2d :: proc(width, height: ui.Size_Percentage, config: ui.ElementConfiguration, value: ^v2, min: f32, max: f32, allocator := context.temp_allocator) -> ^ui.Element {
 	container := ui.container_begin(dimensions = {width, height}, config = config)
 		dimensions := ui.Dimensions {ui.Size_Percentage(0.5), ui.Size_Percentage(1.0)}
-		data: ^ElementData_Slider
-		data = new(ElementData_Slider, allocator)
+		data: ^UiElementData_Slider
+		data = new(UiElementData_Slider, allocator)
 		data^ = {value = &value.x, min = min, max = max}
 		ui.slider(dimensions, {margin = config.margin}, data)
 		ui.same_line()
-		data = new(ElementData_Slider, allocator)
+		data = new(UiElementData_Slider, allocator)
 		data^ = {value = &value.y, min = min, max = max}
 		ui.slider(dimensions, {margin = config.margin}, data)
 	ui.container_end()
@@ -127,13 +143,13 @@ ui_slider_2d :: proc(width, height: ui.Size_Percentage, config: ui.ElementConfig
 ui_input_float_2d :: proc(width, height: ui.Size_Percentage, config: ui.ElementConfiguration, value: ^v2, value_string_x, value_string_y: cstring, allocator := context.temp_allocator) -> ^ui.Element {
 	container := ui.container_begin(dimensions = {width, height}, config = config)
 		dimensions := ui.Dimensions {ui.Size_Percentage(0.5), ui.Size_Percentage(1.0)}
-		data: ^ElementData_FloatInput
-		data = new(ElementData_FloatInput, allocator)
+		data: ^UiElementData_FloatInput
+		data = new(UiElementData_FloatInput, allocator)
 		data^ = {value_string = value_string_x, value = &value.x}
 		ui.input_float(dimensions, {margin = config.margin}, data)
 		ui.same_line()
 
-		data = new(ElementData_FloatInput, allocator)
+		data = new(UiElementData_FloatInput, allocator)
 		data^ = {value_string = value_string_x, value = &value.x}
 		ui.input_float(dimensions, {margin = config.margin}, data)
 	ui.container_end()
@@ -145,15 +161,36 @@ render_ui_elements :: proc(ctx: ^ui.Context, elements: []ui.Element) {
 		area := rl.Rectangle(element.area)
 		switch element.type {
 		case .Container:
-			rl.DrawRectangleRounded(area, 0.1, 4.0, {0, 0, 0, 192})
-			rl.GuiGroupBox(area, element.label)
+			dim := rl.Color {0, 0, 0, 192}
+			if element.data != nil {
+				data := cast(^UiElementData_Container)element.data
+				switch data.type {
+				case .Normal:
+					rl.DrawRectangleRounded(area, 0.1, 4.0, dim)
+					rl.GuiGroupBox(area, element.label)
+				case .Matrix:
+					matrix_area := ui.rect_grow(ui.get_element_outer_area(element), -data.thickness * 2.0)
+					tl, tr, br, bl := ui.rect_get_corners(matrix_area)
+					col := rl.WHITE
+					hook_length: f32 = 4.0
+					rl.DrawLineEx(tl, bl, data.thickness, col)
+					rl.DrawLineEx(tl, tl + V2_RIGHT * hook_length, data.thickness, col)
+					rl.DrawLineEx(bl, bl + V2_RIGHT * hook_length, data.thickness, col)
+					rl.DrawLineEx(tr, br, data.thickness, col)
+					rl.DrawLineEx(tr, tr + V2_LEFT * hook_length, data.thickness, col)
+					rl.DrawLineEx(br, br + V2_LEFT * hook_length, data.thickness, col)
+				}
+			} else {
+				rl.DrawRectangleRounded(area, 0.1, 4.0, dim)
+				rl.GuiGroupBox(area, element.label)
+			}
 		case .Button:
 			rl.GuiButton(area, element.label)
 		case .Slider:
-			data := cast(^ElementData_Slider)element.data
+			data := cast(^UiElementData_Slider)element.data
 			rl.GuiSlider(area, "", "", data.value, data.min, data.max)
 		case .InputFloat:
-			data := cast(^ElementData_FloatInput)element.data
+			data := cast(^UiElementData_FloatInput)element.data
 			if rl.GuiValueBoxFloat(area, element.label, data.value_string, data.value, ui.is_element_focused(ctx, element)) == 1 {
 				ui.focus_element(ctx, element)
 			}
diff --git a/ui.odin b/ui.odin
index 283b8b2..66557fe 100644
--- a/ui.odin
+++ b/ui.odin
@@ -11,6 +11,9 @@ rect_get_tr :: #force_inline proc(rect: rect2) -> v2 {return {rect.x + rect.widt
 rect_get_br :: #force_inline proc(rect: rect2) -> v2 {return {rect.x + rect.width, rect.y + rect.height}}
 rect_get_bl :: #force_inline proc(rect: rect2) -> v2 {return {rect.x, rect.y + rect.height}}
 rect_get_size :: #force_inline proc(rect: rect2) -> v2 {return {rect.width, rect.height}}
+rect_get_corners :: #force_inline proc(rect: rect2) -> (tl, tr, br, bl: v2) {
+	return rect_get_tl(rect), rect_get_tr(rect), rect_get_br(rect), rect_get_bl(rect)
+}
 rect_grow :: proc(rect: rect2, amount: v2) -> rect2 {return {rect.x - amount.x / 2.0, rect.y - amount.y / 2.0, rect.width + amount.x, rect.height + amount.y}}
 
 ctx: ^Context
@@ -127,9 +130,9 @@ focus_next_element :: proc(ctx: ^Context, allowed_focus := element_type_input) {
 	ctx.element_focus_id = -1
 }
 
-container_begin :: proc(dimensions: Dimensions, config: ElementConfiguration) -> ^Element {
+container_begin :: proc(dimensions: Dimensions, config: ElementConfiguration, data: rawptr = nil) -> ^Element {
 	area := _resolve_element_area(dimensions, config.margin)
-	element := _append_element({area = area, config = config, type = .Container, dimensions = dimensions})
+	element := _append_element({area = area, config = config, type = .Container, dimensions = dimensions, data = data})
 	container_index := len(ctx.elements) - 1
 	append(&ctx.containers, container_index)
 	append(&ctx.container_last_element, -1)
@@ -171,22 +174,22 @@ assert_no_dimensions_percentage_in_auto_container :: proc(dimensions: Dimensions
 	}
 }
 
-button :: proc(dimensions: Dimensions, config: ElementConfiguration) -> ^Element {
+button :: proc(dimensions: Dimensions, config: ElementConfiguration, data: rawptr = nil) -> ^Element {
 	assert_no_dimensions_percentage_in_auto_container(dimensions)
 	area := _resolve_element_area(dimensions, config.margin)
-	return _append_element({area = area, config = config, type = .Button, dimensions = dimensions})
+	return _append_element({area = area, config = config, type = .Button, dimensions = dimensions, data = data})
 }
 
-slider :: proc(dimensions: Dimensions, config: ElementConfiguration, data: rawptr) -> ^Element {
+slider :: proc(dimensions: Dimensions, config: ElementConfiguration, data: rawptr = nil) -> ^Element {
 	assert_no_dimensions_percentage_in_auto_container(dimensions)
 	area := _resolve_element_area(dimensions, config.margin)
-	return _append_element({area = area, config = config, type = .Slider, data = data, dimensions = dimensions})
+	return _append_element({area = area, config = config, type = .Slider, dimensions = dimensions, data = data})
 }
 
-input_float :: proc(dimensions: Dimensions, config: ElementConfiguration, data: rawptr) -> ^Element {
+input_float :: proc(dimensions: Dimensions, config: ElementConfiguration, data: rawptr = nil) -> ^Element {
 	assert_no_dimensions_percentage_in_auto_container(dimensions)
 	area := _resolve_element_area(dimensions, config.margin)
-	return _append_element({area = area, config = config, type = .InputFloat, data = data, dimensions = dimensions})
+	return _append_element({area = area, config = config, type = .InputFloat, dimensions = dimensions, data = data})
 }
 
 get_element_outer_area :: proc(element: Element) -> rect2 {