diff --git a/addons/material_maker/main_window.tscn b/addons/material_maker/main_window.tscn
index d3ad15d..356b3b6 100644
--- a/addons/material_maker/main_window.tscn
+++ b/addons/material_maker/main_window.tscn
@@ -1,4 +1,4 @@
-[gd_scene load_steps=13 format=2]
+[gd_scene load_steps=11 format=2]
 
 [ext_resource path="res://addons/material_maker/main_window.gd" type="Script" id=1]
 [ext_resource path="res://addons/material_maker/library.tscn" type="PackedScene" id=2]
@@ -9,18 +9,6 @@
 [ext_resource path="res://addons/material_maker/icons/icons.svg" type="Texture" id=7]
 [ext_resource path="res://addons/material_maker/node_factory.gd" type="Script" id=8]
 
-[sub_resource type="Shader" id=1]
-code = "shader_type canvas_item;
-
-uniform sampler2D tex;
-
-void fragment() {
-	COLOR = texture(tex, UV);
-}"
-
-[sub_resource type="ShaderMaterial" id=2]
-shader = SubResource( 1 )
-
 [sub_resource type="AtlasTexture" id=3]
 flags = 4
 atlas = ExtResource( 7 )
@@ -111,7 +99,10 @@ margin_bottom = 684.0
 tab_align = 0
 
 [node name="Preview2D" parent="VBoxContainer/HBoxContainer/VBoxContainer/Preview" instance=ExtResource( 3 )]
-material = SubResource( 2 )
+margin_left = 4.0
+margin_top = 32.0
+margin_right = -4.0
+margin_bottom = -4.0
 rect_min_size = Vector2( 250, 250 )
 
 [node name="Preview3D" parent="VBoxContainer/HBoxContainer/VBoxContainer/Preview" instance=ExtResource( 4 )]
diff --git a/addons/material_maker/preview/preview_2d.gd b/addons/material_maker/preview/preview_2d.gd
index 1cba73f..f687363 100644
--- a/addons/material_maker/preview/preview_2d.gd
+++ b/addons/material_maker/preview/preview_2d.gd
@@ -1,7 +1,8 @@
+tool
 extends ColorRect
 
-func _ready() -> void:
-	material = material.duplicate(true)
-
 func set_preview_texture(tex: Texture) -> void:
 	material.set_shader_param("tex", tex)
+
+func on_resized() -> void:
+	material.set_shader_param("size", rect_size)
diff --git a/addons/material_maker/preview/preview_2d.tscn b/addons/material_maker/preview/preview_2d.tscn
index 3073c0f..3302b2e 100644
--- a/addons/material_maker/preview/preview_2d.tscn
+++ b/addons/material_maker/preview/preview_2d.tscn
@@ -6,24 +6,30 @@
 code = "shader_type canvas_item;
 
 uniform sampler2D tex;
+uniform vec2 size;
 
 void fragment() {
-	COLOR = texture(tex, UV);
+	float ms = max(size.x, size.y);
+	vec2 uv = fract(0.5+1.2*(UV-vec2(0.5))*ms/size.yx);
+	vec2 m2 = min(fract(uv), 1.0-fract(uv));
+	COLOR = mix(texture(tex, uv), vec4(0.0, 1.0, 0.0, 1.0), step(min(m2.x, m2.y), 1.0/min(size.x, size.y)));
 }"
 
 [sub_resource type="ShaderMaterial" id=2]
 shader = SubResource( 1 )
+shader_param/size = Vector2( 371, 198 )
 
 [node name="Preview2D" type="ColorRect"]
 material = SubResource( 2 )
 anchor_right = 1.0
 anchor_bottom = 1.0
-margin_left = 4.0
-margin_top = 32.0
-margin_right = -4.0
-margin_bottom = -4.0
+margin_left = 17.0
+margin_top = 17.0
+margin_right = -892.0
+margin_bottom = -505.0
 rect_min_size = Vector2( 64, 64 )
 mouse_filter = 1
 size_flags_horizontal = 0
 size_flags_vertical = 8
 script = ExtResource( 1 )
+[connection signal="resized" from="." to="." method="on_resized"]