| 482 |   |  1. Introduce zoom in/out functionality of the viewer by adding mouse wheel events to the end of `mouse()` | 
                      
                      
                        |   | 482 |  1. OK, it rotates. But how come the light rotates with the teapot? I'm pretty sure that the light is not rotated while the teapot vertices are. Answer: Take a look into the `normal`. You need to rotate the vertex normal in the `vertex_shader[]` too! With a code like: | 
                      
                        |   | 483 |   {{{ | 
                      
                        |   | 484 |   #!c | 
                      
                        |   | 485 |   vec4 n = RotationMatrix*vec4(gl_NormalMatrix*gl_Normal, 1);\ | 
                      
                        |   | 486 |   normal=normalize(n.xyz); | 
                      
                        |   | 487 |   }}} | 
                      
                        |   | 488 |  2. Introduce zoom in/out functionality of the viewer by adding mouse wheel events to the end of `mouse()` |