Support
Contact and FAQ for the KIKARAKU app
Frequently Asked Questions
Q. Which devices are supported?
iPhone / iPad with iOS 15.0 or later, and Android phones and tablets with Android 7.0 (API level 24) or later.
Q. Is the app paid?
No. The app is free, with no in-app purchases, subscriptions, or paid content unlocks, and no account is needed.
Q. Does it work offline?
All features except ads work offline.
Q. What about ads?
A Pangle banner ad is shown at the bottom of the screen, and a full-screen (interstitial) ad may be shown when you clear a stage and return to the stage list (including when you leave a stage during the comprehension check). There is no paid option to remove ads. You can turn off personalized ads in "About this app" > "Ad settings" (on iOS, this appears after you have answered the tracking dialog). See the Privacy Policy for details.
Q. I don't see any ads.
Ads may not appear when you are offline or on an unstable connection, when no ad is available at that moment, or right after launch while ads are still loading. On iOS no ads are loaded until you answer the tracking dialog, and on Android none are loaded until you answer the first-launch ad question. Everything in the app works normally without ads; this is not a bug.
Q. How do I change the language?
The app supports 74 languages, including English and Japanese, and follows your device language automatically. To use a different language just for this app, on iPhone / iPad go to Settings > Apps > KIKARAKU > Language; on Android 13 or later go to Settings > System > Languages > App languages > KIKARAKU (names and locations vary by OS version and device).
Q. How do I switch between dark and light mode?
Tap the theme button at the top right of the home screen to switch between the dark and light themes. Dark is the default, and your choice is kept the next time you open the app.
Q. Can I quit during the comprehension check?
Yes. If you tap the back button at the top left during the comprehension check (or press the back key on Android), the app asks "Leave this stage?". Choose "Leave stage" to return to the stage list (as when you clear a stage, a full-screen ad may be shown). During the intuition quiz, hands-on and explanation phases, the back button takes you straight back to the stage list.
Q. Is my progress saved? How do I reset it?
Cleared stages are saved on your device, and the home screen shows a "Cleared" mark and your progress. You can replay any stage from the start at any time. To erase the record completely, delete the app's data: on iPhone / iPad, delete and reinstall the app; on Android, go to Settings > Apps > KIKARAKU > Storage & cache > Clear storage. This also resets your theme and personalized-ads choice. The record is never sent to our servers, so we cannot restore it.
Q. Can I use it in class?
Yes. Feel free to use it in schools, tutoring, or self-study. Every puzzle can be solved with middle- and high-school geometry.
Q. In the rope-around-the-Earth stage, the gap doesn't change when I change the size of the Earth.
That is not a bug; it is the answer. The circumference is 2πr, so adding 1 m of rope increases the radius by 1/2π m (about 16 cm), whatever the original radius. The explanation phase shows why your intuition and the answer disagree.
Reporting Bugs
To help us resolve issues quickly, please include:
- Device name (e.g. iPhone 16 / Pixel 10a)
- OS version (e.g. iOS 26.1 / Android 16)
- App version (e.g. 4.0.0, shown in "About this app")
- The stage where it happened, a description and reproduction steps
About the App
KIKARAKU is an educational entertainment app for experiencing 14 geometry puzzles that defy intuition, including the sum of exterior angles, the rope around the Earth, the Reuleaux triangle, Buffon's needle and Gabriel's horn, in four phases: an intuition quiz, hands-on play, the explanation, and a comprehension check.
Version: 4.0.0