Todos:
1. test on other systems

Desired features:
1. change zoom to (or add) step forward
2. print menu on screen and terminal
4. picking mechanism
5. rotation and scaling in 2D window
6. draw shadows

Known Issues:
1. screen capturing doesn't support window resizing
2. screen capturing doesn't support 2D drawing of strings
3. screen capturing not in 2D window
4. multiple windows cannot communicate (simultaneous refresh)
5. multiple windows will be closed together
6. not detecting key up event of special keys (does glut support it?)
