Digital Store with Points

Is it possible to have a digital store with OpenCart that will list the prices with POINTS?

For example:
How to publish your book - PDF - costs 5 POINTS
Best Fast Cooking Tips - PDF - 3 POINTS

Where each 2 points is 1$

Then the customer can buy 10 or 20 Points that he can spend on digital items?

he can NOT buy the item directly unless he has enough points.

Hope I made myself clear

Anticipated thanx for the reply