OpenGL Lighting

WARNING: The timer function sometimes returns only negative values leading the sphere not to jump up and down properly. You may want to fix this first.
TODO: With this code you can learn a lot about lighting and materials. Here are some ideas for you to experiment with.
- Make at least 3 sphere jump up and down
- Make a directional and a positional light source
- Find out about spotlights in OpenGL and implement one of those
- Let the spotlight jump up and down as well
- Experiment with material properties. Make one sphere that's metallic looking.
- Do some physics. Let the spheres have some acceleration.
- Squish the spheres when they hit the ground. Make sure to take care of the normals when scaling!
If you did something cool, send me the code and I'll make a best-of presentation in one of the labs.