Mahjong Helper & Calculator boasts a variety of features designed to enhance the Mahjong playing experience. One standout feature is the Hand Scorer and Calculator, which includes an easy-to-use tile selection system that allows players to calculate hand values effortlessly. This feature supports various rule sets such as European Classical, Hong Kong, Japanese Modern with Dora tiles and Red Fives, and Chinese Official MCR/Competition rules.

In addition to scoring, the app offers 4, 3, and 2 player scoring modes, catering to different play styles. Players can send scores directly from the Hand Scorer to the Score Sheet or enter them manually. The Score Sheet not only calculates payments but also supports 'Ready' declarations and counters in Japanese Mahjong. With cross-device sharing capabilities, players can keep records and contribute to scoring from their own devices, provided there's a data connection.

Mahjong Helper & Calculator offers a diverse range of content that caters to both beginners and experienced Mahjong players. The app supports multiple scoring systems including European Classical, Hong Kong, Japanese Modern / EMF Riichi, and Chinese Official (MCR / Competition), ensuring that users from different regions can enjoy the game according to their local rules.

One of the key features is its Hand Scorer / Calculator with an intuitive tile/set-type selector, which simplifies the process of calculating hand values. This tool not only makes gameplay smoother but also adds an educational aspect for those learning the intricacies of Mahjong scoring. Additionally, the app provides beautiful, easy-to-read tiles that enhance the visual experience and make it more engaging for users.

The application goes beyond just scoring by offering functionalities such as tracking match history, experimenting with different scoring methods, and supporting seat rotation between rounds. These features ensure that the content remains fresh and dynamic, encouraging continued use and exploration within the app.

User engagement in Mahjong Helper & Calculator is significantly boosted by its comprehensive set of tools designed to keep players invested in their games. With support for 4, 3, and 2 player scoring modes, along with detailed score sheets that calculate payments between players, the app ensures that every session is interactive and fair.

A standout feature is the ability to share matches across devices, allowing other players to keep a record of the match and contribute to scoring from their own Android or iOS devices. This social aspect enhances user retention as friends and family can participate together even when they're not physically present in the same location.

To further aid retention, the app includes a 'Scoring' panel where users can see how scores are calculated step-by-step. This transparency helps build trust and understanding among users, making them more likely to return to the app for future games. By combining these elements, Mahjong Helper & Calculator successfully maintains high levels of user engagement and long-term retention.