def shader():
    vertex_shader = """
        #version 450 core
            layout (location = 0) in vec3 position;
            layout (location = 1) in vec3 color;
            layout (location = 2) in vec2 texCoord;
            layout (location = 3) in vec3 normal;
            uniform mat4 transform;
            out vec4 pos;
            out vec3 ourColor;
            out vec2 TexCoord;
            out vec3 norm;
            void main()
            {
            gl_Position = transform * vec4(position.x, position.y, position.z, 1.0f);
            pos = gl_Position;
            ourColor = color;
            TexCoord = vec2(texCoord.x, texCoord.y);
            norm = (transform * vec4(normal, 0.0)).xyz;
            }
        """

    fragment_shader = """
        #version 450 core
            in vec4 pos;
            in vec3 ourColor;
            in vec2 TexCoord;
            in vec3 norm;
            out vec4 color;
            uniform sampler2D texture1;
            uniform bool flag;
            uniform vec4 l_pos;
            uniform vec4 l_amb;
            uniform vec4 l_diff;
            uniform vec4 l_spec;
            uniform float l_shine;
            void main()
            {
            vec3 L = normalize(l_pos.xyz - pos.xyz);
            vec3 E = normalize(vec3(0, 0, -1)-pos.xyz);
            vec3 R = normalize(-reflect(L, norm));
            vec4 Iamb  = l_amb;
            vec4 Idiff = l_diff * max(dot(norm, L), 0.0);
            Idiff = clamp(Idiff, 0.0, 1.0);
            vec4 Ispec = l_spec * pow(max(dot(R, E), 0.0), l_shine);
            Ispec = clamp(Ispec, 0.0, 1.0);
            if (flag){
                color = vec4(ourColor, 1.0f);
                }
            else {
            color = texture(texture1, TexCoord);
                }
            color = color * (Iamb + Idiff + Ispec);
            }
        """
    global shader
    shader = OpenGL.GL.shaders.compileProgram(OpenGL.GL.shaders.compileShader(vertex_shader, GL_VERTEX_SHADER),
                                              OpenGL.GL.shaders.compileShader(fragment_shader, GL_FRAGMENT_SHADER))

    buildVAO()