How does the puzzle rating work?

The system’s technical term is called Glicko-2. It starts at 1200. Only Journey puzzles affect it – each solve or fail is scored as a game and adjusts your rating up or down. Your rating determines which Journey tier/level bands and which Rush/Survival difficulty band you’re served.

Glicko-2 is more modern and complex than pure Elo, because it takes more variables into account, like uncertainty and volatility. In practice, you don’t need to worry about these. Just have fun!