yhtz - a yahtzee CLI game with 8 bytes of state

Inspired by The Bitwise Gamedev Challenge. Not sure if this technically counts since there aren't really "frames", but the spirit of the challenge is there -- the game should be able to be picked up at any point using the single 8 byte state struct.

State layout

Byte 1

• Roll count: 2 bits (high)
• "Top" section flags: 6 bits, one for each number, indicating whether we've played it yet

    00 000000
roll    ^^ ^^^^^^
count---|| ||||||
           654321

Byte 2

• "Top" rolling score: 7 bits (low)
• High bit is ignored

Byte 3

• "Bottom" section flags: 7 bits (low), one for each category
• High bit is ignored

Byte 4

• "Bottom" rolling score: 8 bits

Bytes 5-6

• Dice: 5 total dice, each die has 3 bits, representing their current value
• High bit is ignored

x 000 000 000 000 000
  D4. D3. D2. D1. D0.

Bytes 7-8

• Seed: a 16-bit unsigned integer representing the seed for the random number generator. Uses Dr. Lemire's 16-bit WyHash example.