ios https://apps.apple.com/us/app/skritter-chinese/id520277126?fbclid=IwAR2smCqmd94xSowvn8E8h7e11ClhMO8wB0dCXGVnBGGVwc5nDuL0srwjfIg
android https://play.google.com/store/apps/details?id=com.inkren.skritter.chinese&hl=en_US&fbclid=IwAR0bMrOeDuDP2hbmamkNfTCopC1atk0zSmIj26Kn-3K9iCB0Uj674DGuCCg