Support
Contact for the KORAKU app
How to contact us
For questions, bug reports or requests about the app, please email us at:
FAQ
Q. Is the app free?
Yes. All features are free. A banner ad (Pangle) is shown at the bottom of the screen. There are no in-app purchases or subscriptions.
Q. Which devices are supported?
iPhone and iPad with iOS 15.0 or later, and Android phones and tablets with Android 7.0 (API 24) or later.
Q. How do I change the personalized-ads setting?
Open "About" in the top right of the home screen and choose "Ad settings". On iOS, the setting in Settings > Privacy & Security > Tracking also applies.
Q. Do I need an internet connection?
The simulations work offline. An internet connection is needed only to show ads.
Q. How accurate are the physics calculations?
The simulations are based on the laws of physics with an accuracy suitable for learning. Some calculations are simplified so they can run in real time.
Q. What is the RAKU series?
SUUGAKU, BUTURAKU, HARAKU and others form a series of math and science simulation apps developed by Fuji Bit Inc. KORAKU is its optics edition.
Reporting a problem
When reporting a problem, the following information helps us fix it quickly.
- Your device model (e.g. iPhone 16)
- OS version (e.g. iOS 18.2)
- What happened and how to reproduce it
About the app
KORAKU is an interactive optics simulator for exploring how light travels and where colors come from. It has 12 modes: lens, spherical mirror, eye and glasses, prism, optical fiber, diffraction grating, thin-film interference, polarization, color mixing, rainbow, blue sky and sunset, and the photoelectric effect. It is available in 73 languages, including English and Japanese.
Version: 6.0.0