What's your favorite free programming environment for commonly used smartphones?

I don't have a favorite. I do not feel like anyone that I am aware of has made proper investment to make a quality development app for mobile due to the low market demand. While development is better than on a calculator I think they are below my expectations.

> What's your favorite free programming environment for commonly used smartphones?

Termux

  pkg install python
  python
  print('hello')
  ctrl+D

Haven't tried these, but have seen them recommended:

Acode

Termux + neovim

Termux + code-server (vscode-like, accessed through phone browser at localhost)

I like Codea for iOS, though the free version has a soft-limit at 500 lines. If a project gets bigger than 500 lines you can still run code but it'll nag you to upgrade.

Current smartphones are highly optimized for content consumption a.k.a doom scrolling. Nothing serious exists for programming. On top of that, a touch keyboard and hard to reach special characters make programming on a modern smartphone a big chore. I miss the old days of smartphones that had a hardware keyboard with tactile feedback. I used to code up and maintain a PHP based dynamic website circa 2007 with a Sony Ericsson K770i and upload through a J2ME based FTP client that also had the text editor in it. If I remember it correctly it was called MobyExplorer

It's much harder to type on a TI calculator than a smartphone.

Not sure I agree. You can "blind type" on a physical keyboard, and even if it has less sophistication in the way of inputting large amounts of text (lack of auto complete, lack of fuzzy typing/auto correct), a calculator is purpose built with tons of shortcuts and contextual menus that you access from muscle memory without second guessing yourself. Right now, if I've got a mildly complicated mathematical expression to type, I'd rather do it on a last-century calculator rather than e.g. on Android's GeoGebra.

It's been a long time since I've done it, but I could type pretty quickly on a TI-83 - even with the silly ABC keyboard layout and all.

I did, in Java 2ME for my Nokia. That was a completely different experience and much harder to get going. I did make a color 2D game though in about a week.

The TI-200 was much more accessible and fun, creating small little programs during or after class. Only once you wanted to go assembly did it become a chore again.

To summarize: not the same.