It sounds like you're describing the samba drum, particularly the surdo or tamborim, which are iconic musical instruments in Brazil and deeply rooted in samba music—a genre central to Brazilian culture, especially during Carnival.

However, based on your mention of it being "commonly played by everyone there" and usable offline in an app, you might be referring to a digital instrument app that simulates a traditional Brazilian instrument—possibly one that includes realistic sounds of the cuíca, surdo, agogô, or tamborim.

The cuíca, in particular, is a friction drum that's very popular in Brazil and known for its unique, vocal-like sound. It's often played by both professionals and amateurs, and many mobile apps now feature it as a central instrument.

Given your note about version 1.3 released on July 31, 2018, with a new background, it's likely this is a mobile app like:

• "Brazilian Drums – Samba Music App"
• "Cuíca Drum Player"
• "Samba Rhythm Machine"

These apps often include:

• Authentic Brazilian drum sounds
• Offline functionality (no internet needed)
• Easy-to-use interface for beginners
• Customizable backgrounds (as mentioned in the update)
• Educational features for rhythm and music

Summary:
You're likely referring to a digital instrument app featuring a traditional Brazilian drum, such as the cuíca or tamborim, designed to be accessible to everyone and playable offline—with the latest update (v1.3) adding a new background theme.

If you’re looking for a real-world instrument, the cuíca is one of the most iconic and widely played in Brazil. But if it's an app, then it's most likely a musical instrument simulator with authentic Brazilian rhythms and a user-friendly design.