The system will randomly generate two number squares in two empty cells, with a high probability of 2 and a low probability that one of them may be 4.
Every time you slide, all the blocks will move in the direction you specify.
Trigger condition: During a movement, if two blocks with the same number collide due to movement, they will merge.
Merge result: These two blocks will be merged into a brand new block, and the number of the new block is the sum of the numbers of the original two blocks (e.g. 2+2=4, 4+4=8, 8+8=16).