Cardinal Chains is a minimalistic puzzle in which you have to walk through every single cell of the board. The only rule is you can only move to a cell containing same or bigger number. You cannot go back.
The game has 313 different levels. It will only be a single starting point in the first ones, but as soon as you go further into the game, you will need to combine several of them in order to beat them.
Use following keys in order to move through the board:
O - Left
P - Right
Q - Up
A - Down
N/M, K/L - Cycle through starting points, if any R - Restart level, in case you got stuck.
T - Back to main menu.
None of these options ask for confirmation, so be careful.