There are more possible moves, and so I think more "outs" for a long time in the beginning of the game. I think the game has a more gradual difficulty curve.
When the board is empty, you'll start and gain 1, 2, 4, 8, etc. pieces. You can often make pieces to combine with those easily, since you can move in any direction and the board is relatively empty.
Eventually, over time, larger pieces build up. 64, 128, 256, etc. You can't make such large numbers easily, and they'll start to be cluttered around and in between other numbers. When the board becomes congested, and when there are many different numbers in play, the challenge ramps up.
When the board is empty, you'll start and gain 1, 2, 4, 8, etc. pieces. You can often make pieces to combine with those easily, since you can move in any direction and the board is relatively empty.
Eventually, over time, larger pieces build up. 64, 128, 256, etc. You can't make such large numbers easily, and they'll start to be cluttered around and in between other numbers. When the board becomes congested, and when there are many different numbers in play, the challenge ramps up.