u64 implementation

[Incompleteusern]

Currently, the grid used for searching

type Grid = [[u8; 4]; 4];

is stored as an array of u8s.

In normal 2048, the max score is $2^{17}$. An adversarial opponent can likely guarantee that even $2^{16}$ is unobtainable, so its possible to reduce the grid to being one u64 to halve memory usage as it stands right now.

This also allows for replacing the array calls with bit manipulations, which is probably also faster.

[howard36]

Yeah, this is a good optimization.

But FYI, I'm not actively working on this project at the moment, so don't expect any changes for a while. For now I'll add it to my todo list that keeps growing