This example demonstrates a spot light and its effect upon a tesselated plane
The controls move the spotlight and adjust its cone angle, etc.  A red arrow
icon shows the position and orientation of the spotlight.  By moving and
rotating the spotlight, the expected lighting patterns (circles, ellipses and
parabolas) may be seen

The key commands are:

i, k - translate light in x
j, l - translate light in y
u, o - rotate light around z axis
Space - reset transforms
q, w - increase, decrease spotlight cone angle
w, s - increase, decrease the spotlight attenuation exponent
