Phase 09: Reinforcement Learning

RL for Games — AlphaZero, MuZero, and the LLM-Reasoning Era

1992: TD-Gammon beat human champions at backgammon with pure TD. 2016: AlphaGo beat Lee Sedol. 2017: AlphaZero dominated chess, shogi, and Go from scratch. 2024: DeepSeek-R1 proved the same recipe, with GRPO replacing PPO, works on reasoning. Games are the benchmark that drives every breakthrough in this phase. Games have everything RL wants. Clean reward (win/loss). Infinite episodes (self-play resets). Perfect simulation (the game is the simulator). Discrete or small continuous action spaces. Multi-agent structure that forces adversarial robustness. And games are how every major RL breakthrough was tested. TD-Gammon (backgammon, 1992). Atari-DQN (2013). AlphaGo (2016). AlphaZero (2017). OpenAI Five (Dota 2, 2019). AlphaStar (StarCraft II, 2019). MuZero (learned model, 2019). AlphaTensor (matrix multiplication, 2022). AlphaDev (sorting algorithms, 2023). DeepSeek-R1 (math reasoning, 2025) — the latest demonstration that game-RL techniques work on text. This capstone surveys the three landmark architectures — AlphaZero, MuZero, and GRPO — through a single unifying lens: self-play + search + policy improvement. Each generalizes the previous; GRPO in particular is AlphaZero's recipe applied to LLM reasoning, with tokens as actions and mathematical verification as the win signal. AlphaZero ↔ MuZero ↔ GRPO: same loop, different environments The unifying loop. AlphaZero (2017). Silver et al. Given a game (chess, shogi, Go) with known rules: Policy-value network: one tower fθ(s) → (p, v). p is a prior…

RL for Games — AlphaZero, MuZero, and the LLM-Reasoning Era: 1992: TD-Gammon beat human champions at backgammon with pure TD. 2016: AlphaGo beat Lee Sedol.…

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