diff --git a/gui/panel.go b/gui/panel.go
index 8efe28f5..07765d5c 100644
--- a/gui/panel.go
+++ b/gui/panel.go
@@ -98,7 +98,8 @@ type Panel struct {
 		paddingsColor math32.Color4  // panel padding color
 		contentColor  math32.Color4  // panel content color
 		textureValid  float32        // texture valid flag (bool)
-		dummy         [3]float32     // complete 8 * vec4
+		opacity       float32
+		dummy         [2]float32 // complete 8 * vec4
 	}
 }
 
@@ -135,6 +136,7 @@ func (p *Panel) Initialize(ipan IPanel, width, height float32) { // TODO rename
 
 	p.width = width
 	p.height = height
+	p.udata.opacity = 1
 
 	// If first time, create panel quad geometry
 	if panelQuadGeometry == nil {
@@ -393,6 +395,22 @@ func (p *Panel) Paddings() RectBounds {
 	return p.paddingSizes
 }
 
+// SetOpacity sets the alpha modifier of this panel
+func (p *Panel) SetOpacity(alpha float32) {
+	if alpha > 1 {
+		alpha = 1
+	}
+	if alpha < 0 {
+		alpha = 0
+	}
+	p.udata.opacity = alpha
+}
+
+// Opacity returns current opacity value
+func (p *Panel) Opacity() float32 {
+	return p.udata.opacity
+}
+
 // SetBordersColor sets the color of this panel borders
 // The borders opacity is set to 1.0 (full opaque)
 func (p *Panel) SetBordersColor(color *math32.Color) {
diff --git a/renderer/shaders/panel_fragment.glsl b/renderer/shaders/panel_fragment.glsl
index cb5b590f..0e2a5777 100644
--- a/renderer/shaders/panel_fragment.glsl
+++ b/renderer/shaders/panel_fragment.glsl
@@ -23,6 +23,7 @@ uniform vec4 Panel[8];
 #define PaddingColor	Panel[5]		  // panel padding color
 #define ContentColor	Panel[6]		  // panel content color
 #define TextureValid	bool(Panel[7].x)  // texture valid flag
+#define Opacity         Panel[7].y        // panel alpha modifier
 
 // Output
 out vec4 FragColor;
@@ -103,18 +104,21 @@ void main() {
 		}
 
         FragColor = color;
+        FragColor.a *= Opacity;
         return;
     }
 
     // Checks if fragment is inside paddings area
     if (checkRect(Padding)) {
         FragColor = PaddingColor;
+        FragColor.a *= Opacity;
         return;
     }
 
     // Checks if fragment is inside borders area
     if (checkRect(Border)) {
         FragColor = BorderColor;
+        FragColor.a *= Opacity;
         return;
     }
 
diff --git a/renderer/shaders/sources.go b/renderer/shaders/sources.go
index f0e3deb3..2b56e069 100644
--- a/renderer/shaders/sources.go
+++ b/renderer/shaders/sources.go
@@ -332,6 +332,7 @@ uniform vec4 Panel[8];
 #define PaddingColor	Panel[5]		  // panel padding color
 #define ContentColor	Panel[6]		  // panel content color
 #define TextureValid	bool(Panel[7].x)  // texture valid flag
+#define Opacity         Panel[7].y        // panel alpha modifier
 
 // Output
 out vec4 FragColor;
@@ -412,18 +413,21 @@ void main() {
 		}
 
         FragColor = color;
+        FragColor.a *= Opacity;
         return;
     }
 
     // Checks if fragment is inside paddings area
     if (checkRect(Padding)) {
         FragColor = PaddingColor;
+        FragColor.a *= Opacity;
         return;
     }
 
     // Checks if fragment is inside borders area
     if (checkRect(Border)) {
         FragColor = BorderColor;
+        FragColor.a *= Opacity;
         return;
     }
 
diff --git a/tools/g3nshaders/main.go b/tools/g3nshaders/main.go
index 2f56d9ce..30795aff 100644
--- a/tools/g3nshaders/main.go
+++ b/tools/g3nshaders/main.go
@@ -20,6 +20,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"text/template"
 )
@@ -163,6 +164,10 @@ func processDir(dir string, include bool) {
 		panic(err)
 	}
 
+	sort.Slice(finfos, func(i, j int) bool {
+		return finfos[i].Name() < finfos[j].Name()
+	})
+
 	// Process all directory entries.
 	for _, fi := range finfos {
 		if fi.IsDir() {