Guess he’s not using an array… IMO with traces you are going to hit a wall when moving the blocks since they need to be checked in order depending on what direction they are told to move.
You can check out this video: Coding Challenge #94: 2048 - Part 1 - YouTube ← even though it’s for Javascript, IMO he does a good job explaining his thought proccess.
You’ll need to know how to navigate a 2d array.