diff --git a/examples/place_texture.gdshader b/examples/place_texture.gdshader
index 95a26f0..282ee69 100644
--- a/examples/place_texture.gdshader
+++ b/examples/place_texture.gdshader
@@ -1,6 +1,7 @@
 shader_type canvas_item;
 
 #include "res://shaderlib/transform.gdshaderinc"
+#include "res://shaderlib/transparency.gdshaderinc"
 
 //!load ./swamp.jpg
 //!load+ img2 ./grass.png
@@ -9,6 +10,6 @@ uniform sampler2D img2: repeat_disable, filter_nearest;
 
 void fragment() {
 	vec4 grass = place_texture(img2, UV, TEXTURE_PIXEL_SIZE, vec2(0, .47), vec2(1));
-	grass.rgb += (vec3(0.03, 0.07, 0.11) - ((UV.y - .8) * 0.15)); // color correction
-	COLOR.rgb = mix(COLOR.rgb, grass.rgb, grass.a);
+	grass.rgb += (vec3(0.02, 0.07, 0.1) - ((UV.y - .8) * 0.15)); // color correction
+	COLOR = alpha_blend(COLOR, grass);
 }
diff --git a/shaderlib/transparency.gdshaderinc b/shaderlib/transparency.gdshaderinc
new file mode 100644
index 0000000..d03949d
--- /dev/null
+++ b/shaderlib/transparency.gdshaderinc
@@ -0,0 +1,9 @@
+
+// Alpha Blending a over b after Bruce A. Wallace
+// sources:
+// - https://en.wikipedia.org/wiki/Alpha_compositing
+vec4 alpha_blend(vec4 b, vec4 a) {
+	float alpha = a.a + (b.a * (1.0 - a.a));
+	vec3 col = ((a.rgb*a.a) + ((b.rgb*b.a) * (1.0 - a.a)) / alpha);
+	return vec4(col.r, col.g, col.b, alpha);
+}
diff --git a/src/Editor.gd b/src/Editor.gd
index d89cdbe..368dcde 100644
--- a/src/Editor.gd
+++ b/src/Editor.gd
@@ -124,11 +124,13 @@ const gdshader_builtins = [
 # shaderlib
 var shaderlib_regex = {
 	"hsv": RegEx.create_from_string(r'\s*\#include\s+\"res\:\/\/shaderlib\/hsv\.gdshaderinc\"'),
-	"transform": RegEx.create_from_string(r'\s*\#include\s+\"res\:\/\/shaderlib\/transform\.gdshaderinc\"')
+	"transform": RegEx.create_from_string(r'\s*\#include\s+\"res\:\/\/shaderlib\/transform\.gdshaderinc\"'),
+	"transparency": RegEx.create_from_string(r'\s*\#include\s+\"res\:\/\/shaderlib\/transparency\.gdshaderinc\"')
 }
 const shaderlib_functions = {
 	"hsv": ["rgb2hsv", "hsv2rgb", "hsv_offset", "hsv_multiply"],
-	"transform": ["place_texture"]
+	"transform": ["place_texture"],
+	"transparency": ["alpha_blend"],
 }
 #
 # configure Highlighter
@@ -182,11 +184,12 @@ func _on_code_edit_code_completion_requested():
 		code_editor.add_code_completion_option(CodeEdit.KIND_FUNCTION, k, k+"(", Color.INDIAN_RED)
 	# shaderlib #
 	var shader_code = code_editor.text
-	for key in shaderlib_functions:
+	for key in shaderlib_regex:
 		if shaderlib_regex[key].search(shader_code) != null:
-			for k in shaderlib_functions[key]:
-				code_editor.code_completion_prefixes.append(k)
-				code_editor.add_code_completion_option(CodeEdit.KIND_FUNCTION, k, k+"(", Color.INDIAN_RED)
+			if key in shaderlib_functions:
+				for k in shaderlib_functions[key]:
+					code_editor.code_completion_prefixes.append(k)
+					code_editor.add_code_completion_option(CodeEdit.KIND_FUNCTION, k, k+"(", Color.INDIAN_RED)
 	# # # # # # #
 	code_editor.update_code_completion_options(true)
 #