diff --git a/progs/demos/fslight.c b/progs/demos/fslight.c
new file mode 100644
index 0000000..1c016cc
--- /dev/null
+++ b/progs/demos/fslight.c
@@ -0,0 +1,334 @@
+/**
+ * Test OpenGL 2.0 vertex/fragment shaders.
+ * Brian Paul
+ * 1 November 2006
+ *
+ * Based on ARB version by:
+ * Michal Krol
+ * 20 February 2006
+ *
+ * Based on the original demo by:
+ * Brian Paul
+ * 17 April 2003
+ */
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/gl.h>
+#include <GL/glut.h>
+#include <GL/glext.h>
+
+static GLfloat diffuse[4] = { 0.5f, 0.5f, 1.0f, 1.0f };
+static GLfloat specular[4] = { 0.8f, 0.8f, 0.8f, 1.0f };
+static GLfloat lightPos[4] = { 0.0f, 10.0f, 20.0f, 1.0f };
+static GLfloat delta = 1.0f;
+
+static GLuint fragShader;
+static GLuint vertShader;
+static GLuint program;
+
+static GLint uLightPos;
+static GLint uDiffuse;
+static GLint uSpecular;
+
+static GLint win = 0;
+static GLboolean anim = GL_TRUE;
+static GLboolean wire = GL_FALSE;
+static GLboolean pixelLight = GL_TRUE;
+
+static GLint t0 = 0;
+static GLint frames = 0;
+
+static GLfloat xRot = 0.0f, yRot = 0.0f;
+
+static PFNGLCREATESHADERPROC glCreateShader_func = NULL;
+static PFNGLSHADERSOURCEPROC glShaderSource_func = NULL;
+static PFNGLGETSHADERSOURCEPROC glGetShaderSource_func = NULL;
+static PFNGLCOMPILESHADERPROC glCompileShader_func = NULL;
+static PFNGLCREATEPROGRAMPROC glCreateProgram_func = NULL;
+static PFNGLDELETEPROGRAMPROC glDeleteProgram_func = NULL;
+static PFNGLDELETESHADERPROC glDeleteShader_func = NULL;
+static PFNGLATTACHSHADERPROC glAttachShader_func = NULL;
+static PFNGLLINKPROGRAMPROC glLinkProgram_func = NULL;
+static PFNGLUSEPROGRAMPROC glUseProgram_func = NULL;
+static PFNGLGETUNIFORMLOCATIONPROC glGetUniformLocation_func = NULL;
+static PFNGLISPROGRAMPROC glIsProgram_func = NULL;
+static PFNGLISSHADERPROC glIsShader_func = NULL;
+static PFNGLUNIFORM3FVPROC glUniform3fv_func = NULL;
+static PFNGLUNIFORM3FVPROC glUniform4fv_func = NULL;
+
+
+
+static void
+normalize(GLfloat *dst, const GLfloat *src)
+{
+   GLfloat len = sqrtf(src[0] * src[0] + src[1] * src[1] + src[2] * src[2]);
+   dst[0] = src[0] / len;
+   dst[1] = src[1] / len;
+   dst[2] = src[2] / len;
+}
+
+
+static void
+Redisplay(void)
+{
+   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+   
+   if (pixelLight) {
+      GLfloat vec[3];
+      glUseProgram_func(program);
+      normalize(vec, lightPos);
+      glUniform3fv_func(uLightPos, 1, vec);
+      glDisable(GL_LIGHTING);
+   }
+   else {
+      glUseProgram_func(0);
+      glLightfv(GL_LIGHT0, GL_POSITION, lightPos);
+      glEnable(GL_LIGHTING);
+   }
+
+   glPushMatrix();
+   glRotatef(xRot, 1.0f, 0.0f, 0.0f);
+   glRotatef(yRot, 0.0f, 1.0f, 0.0f);
+   glutSolidSphere(2.0, 10, 5);
+   glPopMatrix();
+
+   glutSwapBuffers();
+   frames++;
+
+   if (anim) {
+      GLint t = glutGet(GLUT_ELAPSED_TIME);
+      if (t - t0 >= 5000) {
+         GLfloat seconds =(GLfloat)(t - t0) / 1000.0f;
+         GLfloat fps = frames / seconds;
+         printf("%d frames in %6.3f seconds = %6.3f FPS\n",
+                frames, seconds, fps);
+         t0 = t;
+         frames = 0;
+      }
+   }
+}
+
+
+static void
+Idle(void)
+{
+   lightPos[0] += delta;
+   if (lightPos[0] > 25.0f || lightPos[0] < -25.0f)
+      delta = -delta;
+   glutPostRedisplay();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+   glViewport(0, 0, width, height);
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
+   glMatrixMode(GL_MODELVIEW);
+   glLoadIdentity();
+   glTranslatef(0.0f, 0.0f, -15.0f);
+}
+
+
+static void
+CleanUp(void)
+{
+   glDeleteShader_func(fragShader);
+   glDeleteShader_func(vertShader);
+   glDeleteProgram_func(program);
+   glutDestroyWindow(win);
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+  (void) x;
+  (void) y;
+
+   switch(key) {
+   case ' ':
+   case 'a':
+      anim = !anim;
+      if (anim)
+         glutIdleFunc(Idle);
+      else
+         glutIdleFunc(NULL);
+      break;
+   case 'x':
+      lightPos[0] -= 1.0f;
+      break;
+   case 'X':
+      lightPos[0] += 1.0f;
+      break;
+   case 'w':
+      wire = !wire;
+      if (wire)
+         glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+      else
+         glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+      break;
+   case 'p':
+      pixelLight = !pixelLight;
+      if (pixelLight)
+         printf("Per-pixel lighting\n");
+      else
+         printf("Conventional lighting\n");
+      break;
+   case 27:
+      CleanUp();
+      exit(0);
+      break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+SpecialKey(int key, int x, int y)
+{
+   const GLfloat step = 3.0f;
+
+  (void) x;
+  (void) y;
+
+   switch(key) {
+   case GLUT_KEY_UP:
+      xRot -= step;
+      break;
+   case GLUT_KEY_DOWN:
+      xRot += step;
+      break;
+   case GLUT_KEY_LEFT:
+      yRot -= step;
+      break;
+   case GLUT_KEY_RIGHT:
+      yRot += step;
+      break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+Init(void)
+{
+   static const char *fragShaderText =
+      "uniform vec3 lightPos;\n"
+      "uniform vec4 diffuse;\n"
+      "uniform vec4 specular;\n"
+      "varying vec3 normal;\n"
+      "void main() {\n"
+      "   // Compute dot product of light direction and normal vector\n"
+      "   float dotProd = max(dot(lightPos, normalize(normal)), 0.0);\n"
+      "   // Compute diffuse and specular contributions\n"
+      "   gl_FragColor = diffuse * dotProd + specular * pow(dotProd, 20.0);\n"
+      "}\n";
+   static const char *vertShaderText =
+      "varying vec3 normal;\n"
+      "void main() {\n"
+      "   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+      "   normal = gl_NormalMatrix * gl_Normal;\n"
+      "}\n";
+
+
+   const char *version;
+
+   version = (const char *) glGetString(GL_VERSION);
+   if (version[0] != '2' || version[1] != '.') {
+      printf("Warning: this program expects OpenGL 2.0\n");
+      /*exit(1);*/
+   }
+
+
+   glCreateShader_func = (PFNGLCREATESHADERPROC) glutGetProcAddress("glCreateShader");
+   glDeleteShader_func = (PFNGLDELETESHADERPROC) glutGetProcAddress("glDeleteShader");
+   glDeleteProgram_func = (PFNGLDELETEPROGRAMPROC) glutGetProcAddress("glDeleteProgram");
+   glShaderSource_func = (PFNGLSHADERSOURCEPROC) glutGetProcAddress("glShaderSource");
+   glGetShaderSource_func = (PFNGLGETSHADERSOURCEPROC) glutGetProcAddress("glGetShaderSource");
+   glCompileShader_func = (PFNGLCOMPILESHADERPROC) glutGetProcAddress("glCompileShader");
+   glCreateProgram_func = (PFNGLCREATEPROGRAMPROC) glutGetProcAddress("glCreateProgram");
+   glAttachShader_func = (PFNGLATTACHSHADERPROC) glutGetProcAddress("glAttachShader");
+   glLinkProgram_func = (PFNGLLINKPROGRAMPROC) glutGetProcAddress("glLinkProgram");
+   glUseProgram_func = (PFNGLUSEPROGRAMPROC) glutGetProcAddress("glUseProgram");
+   glGetUniformLocation_func = (PFNGLGETUNIFORMLOCATIONPROC) glutGetProcAddress("glGetUniformLocation");
+   glIsProgram_func = (PFNGLISPROGRAMPROC) glutGetProcAddress("glIsProgram");
+   glIsShader_func = (PFNGLISSHADERPROC) glutGetProcAddress("glIsShader");
+   glUniform3fv_func = (PFNGLUNIFORM3FVPROC) glutGetProcAddress("glUniform3fv");
+   glUniform4fv_func = (PFNGLUNIFORM3FVPROC) glutGetProcAddress("glUniform4fv");
+
+   fragShader = glCreateShader_func(GL_FRAGMENT_SHADER);
+   glShaderSource_func(fragShader, 1, &fragShaderText, NULL);
+   glCompileShader_func(fragShader);
+
+   vertShader = glCreateShader_func(GL_VERTEX_SHADER);
+   glShaderSource_func(vertShader, 1, &vertShaderText, NULL);
+   glCompileShader_func(vertShader);
+
+   program = glCreateProgram_func();
+   glAttachShader_func(program, fragShader);
+   glAttachShader_func(program, vertShader);
+   glLinkProgram_func(program);
+   glUseProgram_func(program);
+
+   uLightPos = glGetUniformLocation_func(program, "lightPos");
+   uDiffuse = glGetUniformLocation_func(program, "diffuse");
+   uSpecular = glGetUniformLocation_func(program, "specular");
+
+   glUniform4fv_func(uDiffuse, 1, diffuse);
+   glUniform4fv_func(uSpecular, 1, specular);
+
+   glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
+   glEnable(GL_DEPTH_TEST);
+   glEnable(GL_LIGHT0);
+   glEnable(GL_LIGHTING);
+   glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, diffuse);
+   glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, specular);
+   glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 20.0f);
+
+   printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
+   printf("Press p to toggle between per-pixel and per-vertex lighting\n");
+
+   /* test glGetShaderSource() */
+   {
+      GLsizei len = strlen(fragShaderText) + 1;
+      GLsizei lenOut;
+      GLchar *src =(GLchar *) malloc(len * sizeof(GLchar));
+      glGetShaderSource_func(fragShader, 0, NULL, src);
+      glGetShaderSource_func(fragShader, len, &lenOut, src);
+      assert(len == lenOut + 1);
+      assert(strcmp(src, fragShaderText) == 0);
+      free(src);
+   }
+
+   assert(glIsProgram_func(program));
+   assert(glIsShader_func(fragShader));
+   assert(glIsShader_func(vertShader));
+}
+
+
+int
+main(int argc, char *argv[])
+{
+   glutInit(&argc, argv);
+   glutInitWindowPosition( 0, 0);
+   glutInitWindowSize(200, 200);
+   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
+   win = glutCreateWindow(argv[0]);
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutSpecialFunc(SpecialKey);
+   glutDisplayFunc(Redisplay);
+   if (anim)
+      glutIdleFunc(Idle);
+   Init();
+   glutMainLoop();
+   return 0;
+}
+