flickering triangle (rendering cube)

shaders/fragment.shader

@@ -9,5 +9,5 @@ out vec4 fg_FragColor;
 void main(void)
 {
 //copy-shader
-   fg_FragColor = fg_SmoothColor;
+   fg_FragColor = vec4(0.5,0.5,0.5,1.0);//fg_SmoothColor;
 }

shaders/vertex.shader

@@ -4,17 +4,17 @@
 uniform mat4 fg_ProjectionMatrix;
 
 //vertex-data
-in vec4 fg_Color;
+//in vec4 fg_Color;
 in vec3 fg_VertexIn;
-in vec3 fg_Normal;
+//in vec3 fg_Normal;
 
 //output-data for later stages
-smooth out vec4 fg_SmoothColor;
+//smooth out vec4 fg_SmoothColor;
 
 void main()
 {
    //transform vec3 into vec4, setting w to 1
    vec4 fg_Vertex = vec4(fg_VertexIn, 1.0);
-   fg_SmoothColor = fg_Color + 0.001* fg_Normal.xyzx;
+   //fg_SmoothColor = fg_Color + 0.001* fg_Normal.xyzx;
    gl_Position = fg_ProjectionMatrix * fg_Vertex;
 }