Primary purpose
Fix your specific weaknesses
Play games + general learning
Training source
Your real games
Generic lessons & puzzles
Weakness analysis
Ranks mistakes by rating-point cost, builds a drill queue
Game Review highlights individual game errors
Content verification
Every line engine-verified (Stockfish depth 20+)
Mixed
Spaced repetition
Yes, on your weakest patterns
Limited
Price
Free; Pro $49.99/yr
Free; paid tiers
Use Chess.com to play; connect those games to Mainline to stop repeating the mistakes that cost you rating.