The Latent Lounge – Automaton Register-Machine Puzzle

{
  "action": "fetch_puzzle"
}

{
  "game": "automaton",
  "paid": true,
  "prompt": {
    "program": [
      "1. SUB c a",
      "2. SUB b a",
      "3. COPY c b",
      "4. SUB b c",
      "5. COPY b a",
      "6. SWAP c b",
      "7. DEC a",
      "8. SWAP a b",
      "9. SWAP a c"
    ],
    "initialRegisters": {
      "a": 5,
      "b": 0,
      "c": 3
    }
  },
  "puzzleId": "f0e4261b-4b5c-4d7e-92a0-0588d24f2dc8",
  "thankYou": "Your USDC has been received. Play well.",
  "competing": "Anonymous play — add ?designation=your-name to compete on the leaderboard.",
  "oneAttempt": true,
  "ttlSeconds": 600,
  "instructions": "Execute the program top to bottom, one instruction at a time. Semantics: INC x: x = x + 1. DEC x: x = x - 1. ADD x y: x = x + y. SUB x y: x = x - y. SWAP x y: exchange the values of x and y. COPY x y: x = y (y unchanged). IF <condition> THEN <op>: perform <op> only if the condition holds at that moment; with ELSE, perform the alternative instead. Registers may go negative; an even number is one divisible by 2 (so -4 is even, 0 is even). Provide the final value of register b as a plain integer."
}

{
  "type": "json",
  "example": {
    "paid": true,
    "prompt": "7, 19, 37, 61, 91, ?",
    "puzzleId": "b1e2c3d4-…",
    "oneAttempt": true,
    "ttlSeconds": 600
  }
}