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Main goal: Provide a reasonable way to code on a mobile phone (including a simple IDE).

Language: Roughly based on a Python subset (hence the name). From a language design perspective, it should always be possible to export working Python code, but this feature isn't implemented yet.

Notable differences:

  • Strict type system stealing traits from Rust
  • Explicit variable declarations required (var / const)
  • Blocks terminated by an explict "end" statement (enabling conditions and loops on the command line)
  • Lots of stuff missing

Code examples:

Android Play Store Beta link:


The mobile IDE is not strictly a part of the language, but it’s a feature that sets it apart from other languages: Instead of a text editor, the IDE is based on a line editor that also serves as a shell.

The main motivation for this design is that cursor positioning is extremely fiddly on mobile. A line-based editor splits the editing process up into two separate more reliable steps, limiting position needs to one dimension -- or typing a short command, which allows the user to stay in the keyboard area.

Requiring an explicit “end” statement to close blocks allows the IDE to always automatically indent and format the source code.

A side effect of this design is that this also works quite well for telnet / shell based editing. In particular, explicit block ends allow running arbitrary complex statements from the shell.

Properties and invocations

One special feature of Tantilla is that it parameterless functions and methods are invoked implicitly. Also, assignments to properties are implicity translated to set_<name> if there is no such property.

This makes conversion between properties and setters / getters very simple, at the expense of having a clear distinction between method calls and method references, adding the requirement of a special syntax for function and method references.

Traits instead of Class inheritance

While Tantilla supports classes, there is no support for inheritance between classes. Instead, Traits and Trait implementations ("borrowed" from Rust) can be used for the same purpose.

Standard Library

Apart from some buit-ins borrowed from Python, there is currently only a simple graphics library and an even simpler sound library.

The sound library is just a play function that plays a string in ABC notation, including some limited emoji support for sound effects (at the moment just explosions and shots).

The graphics library consists of a singleton screen object where sprites and text objects can be added, based on the "krash" Android library specifically created for this purpose.

The plan is to move it towards a simple retained mode vector graphics library somewhere in the area of Flash and SVG.

Open Issues


Here, I am leaning towards implementing async/await, again with most details borrowed from Rust.


This is my biggest pain point: How can I limit mutability in a seamless convenient and safe way?

Library support

The foundations should be there, but some practical aspects are missing. Should there be a standard repository? How is it managed? How is it possible to ensure safety for an app rated for kids in the app store?

Standard Library Development

Currently, the graphics library is a strange mix of bitmap and vector API. I am planning to simplify this to vector-only.


Mostly hoping that avoiding traditional OO-inheritence avoids most pain points. Go has done well without so far, so this is not a primary priority at the moment.

Port more "stuff" from Python

Integer type? Not sure what's missing most...


The biggest open issue is probably direction: what matters for the main purpose of the language (mobile programming and a stepping stone from Scratch etal. to Python and/or Rust?