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Thirteen Indian-style mental-math methods that turn 99×99 into a five-second exercise. Ranked from Level 1 to Master 7. No ads, fully offline, ¥350 one-time.
Hey PH 👋
Quick story.
In 2010 there was this Japanese app called Indian Calc Master, made by a small
studio called PandraHouse. It taught you to do mental math the Vedic way —
stuff like 87 × 13, in your head, in a few seconds.
I was a kid when I downloaded it. It wrecked my brain in the best way. I'd do
problems at the dinner table just to freak my parents out.
The app's been gone for years. PandraHouse moved on, the App Store quietly
buried it. I checked once a year for a while, then stopped.
A few months ago I decided to just rebuild it. Same idea, same dojo feel, but
rewritten from zero in Flutter, and translated into 6 languages so it's not
only a Japanese thing anymore.
It's called Way of Indian Math.
The structure is basically the same as the original: 13 techniques, organized
as a martial arts ranking. You start at 6th kyu and work your way up to 7th
dan. Each belt teaches one specific trick — Nikhilam, Urdhva-Tiryagbhyam, the
"tens-match, ones-complement" pattern, and so on. The end goal is solving any
2-digit × 2-digit problem in under 5 seconds.
The Japanese name is 「インド式計算道」, "the way of Indian calculation".
道 (dō) is the same one in 柔道 / 書道 / 茶道. The idea is that this isn't
a feature, it's a practice.
A few choices that mattered to me:
- One-time $3. No ads, no subscription, no signup. Buy it, it's yours.
- Six languages from day one: English, Japanese, Korean, Chinese, French, Spanish.
- Ganesha is still the mascot. The technique is Indian, the original had him,
felt wrong to drop him.
- Fully offline. Nothing leaves the device. Safe to hand to a kid.
I made it on nights and weekends, mostly solo, with a lot of help from Claude Code.
Stuff I'd actually like your honest read on:
1. Does the kyu/dan progression make sense outside Japan, or does it just
feel weird?
2. $3 once, or do people on PH expect free + ads now?
3. If your kid (or you) tried this for a week, what would actually make you
keep coming back?
If you've got a minute, jump straight to 7th dan and try a generic ab × cd
problem cold. Tell me your time, and whether you wanted to throw your phone.
I'll be in the comments all day.
— hiro960
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About Way of Indian Math on Product Hunt
“Solve 87 × 13 in your head. In under 5 seconds.”
Way of Indian Math was submitted on Product Hunt and earned 3 upvotes and 1 comments, placing #147 on the daily leaderboard. Thirteen Indian-style mental-math methods that turn 99×99 into a five-second exercise. Ranked from Level 1 to Master 7. No ads, fully offline, ¥350 one-time.
Way of Indian Math was featured in Education (78.4k followers) on Product Hunt. Together, these topics include over 26.8k products, making this a competitive space to launch in.
Who hunted Way of Indian Math?
Way of Indian Math was hunted by Hirohito Kuromaru. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
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Hirohito Kuromaru