A large share of the teams building on Codename One are banks and financial institutions. They don't ask me for a prettier list component. They ask how to pass a penetration test, what the auditor will want to see, and which protections actually work on which device.

What is Codename One? Codename One is an open-source framework for building native iOS, Android, desktop, and web apps from a single Java or Kotlin codebase. Learn more at codenameone.com .

Bastion is my answer, written as code. It's a virtual bank and a small exchange, the app and its server in one Java project. Customers hold dollars, euros, bitcoin and ether, move money, issue and freeze cards, trade, and withdraw coins to addresses they've allowed in advance. Staff verify the ledger and the audit trail.…