Abacus Trainer: Mental Mathv4.0

What changed

• SocialAdded Daily Challenge mode with a global leaderboard
• SocialAdded friend challenge mode via link sharing
• New featureAdded Sprint mode with timed intervals and difficulty levels
• RetentionAdded progress tracking including streaks and activity heatmaps
• UXAdded soroban technique hints for incorrect answers
• UXCustom Mode now persists user settings between drills

Original release notes

Daily Challenge: one shared problem set every day, with a global leaderboard.
Challenge a friend: send a link and race each other on the same questions.
Sprint: beat the clock over 30 seconds, 1 minute or 2 minutes, at three difficulty levels.
Progress: practice streaks, an activity heatmap, and a breakdown of the problems you keep missing.
Hints: see the soroban technique behind any problem you got wrong.
Custom Mode now remembers your settings between drills.