...The current account balance is calculated based on the SQL operation (Double-entry bookkeeping) Internalization of the application for three languages: English, German and Polish. Support for multiple currencies with the current rate supplied from an external server via API. Application programmed according to the correct design patterns and principle, i.e. SOLID, DRY and KISS. Software supports PWA, it is adapted to all modern browsers and mobile devices (RWD). Implementation of Google Analytics along with the Cookie Consent according to the GDPR.