The first tier (Beginner) is open by default; later tiers unlock once your rating reaches that tier’s floor or you fully clear the previous tier. Within a tier, levels unlock as you clear the one before. A level is “cleared” at 6/8 puzzles solved.
Stars are awarded as follows:
- * for a 6/8 puzzles soved per level.
- ** for 7 or 8 puzzles solved.
- *** 7 or 8 puzzles solved with at least 6 puzzles solved in first try.