About MentalForge

MentalForge builds mental-calculation fluency — the ability to work with numbers quickly in your head. It is one of the two classic mind-sport skills (with memory) that the library was missing.

Two ways to practise

• Sprint — pick add, subtract, multiply or divide and a difficulty, then work eight questions in your head. An abacus pictures each number so you can see it. Beat your own best — the only score that matters.
• Trick lab — learn Vedic and Trachtenberg shortcuts (multiply by 11, square a number ending in 5, subtract from a round number) worked out step by step, then try one yourself.

How it works — and stays honest

• A real engine grades every answer. Every question and every answer is computed by a deterministic maths engine — no AI is ever near the arithmetic, so the grading can’t be wrong.
• On-device, no accounts. Your practice and your personal best live in this browser only; nothing is sent anywhere (no login, no data leaves the device).
• Calm by design. No stress clock, no streaks to protect, no leaderboard. The score you chase is your own previous best.

Honest note: mental calculation is a real, learnable skill worth practising. It is a maths skill — not a shortcut to being “smarter” in general.