It is simple enough. The goal in Luxor is to make matches with your own spheres
and the ones lined up in a moving string. A match can be done when you hit a 
group of 2+ spheres with one of yours being of the same color. The Gods appreciate
when you make several matches in a row and will reward you with a power up when 
you complete your 3rd match in a series. The matches may accumulate beyond 3 so 
you can get a power up after your 6th, 9th, 12th match, etc. But be careful, the
number of matches will get reset 1) if you miss your shot and 2) if you have no 
other choice but to add spheres to singles on a string. At times I find it better
to create pairs into a string before starting to eliminate spheres altogether, 
just so I can get many power ups in a short time.