Here is an excerpt from an email conversation that I had with one of our student's parent:
"While we have lots of books with problems, the one challenge has been that problems in the books are not classified by level of difficulty or arranged in increasing order of difficulty. Much like a weight-lifter gradually increases the weight he lifts, it seems better to move to gradually more difficult problems (instead of jumping to IMO level problems early on)."
In response to the above request we have decided to populate problems from various contests in order of difficulty. Each topic will have five layers of problems with increasing order of difficulty. For example, Layer 5 will have IMO caliber problems (most challenging) while Layer 1 has AMC 8 or similar level of problems (very easy).