I trained a neural network on my Android phone using Pydroid 3 — S-tier, 92% win rate, no servers

I wanted to see if my Android phone could train a real neural network. No cloud, no GPU, no TensorFlow — just Pydroid 3 and pure Python.

**The result:** A Q-learning neural network that reached S-tier in a fighting game and beat scientific algorithms.

**What it does:**

\- ⚔️ Fighting game: 81.2% win rate against 9 different bots (including Minimax)

\- ✊ Rock-Paper-Scissors: 92% against Exp3 and UCB1 (algorithms from research papers)

\- 🎭 Mafia (social game): 40% win rate (2x better than random)

**How it works:**

\- Pure Python lists and loops — no NumPy

\- Manual backpropagation (\~200 lines)

\- Replay Buffer (500 examples)

\- \~75 parameters, model size < 5 KB (JSON)

\- 10,000+ training battles on a phone

**Performance on Android:**

\- 500 fights: \~10 seconds

\- 5,000 RPS rounds: \~30 seconds

\- All trained locally in Pydroid 3

**Why this matters:**

You don't need a gaming PC or cloud GPU to experiment with neural networks. An Android phone is enough to train a working AI that beats algorithms from scientific papers.

Happy to answer questions about training on mobile!

GitHub in comments.

https://redd.it/1u8stc9
@reddit_android