itch.io

They are!  Not yet, it's a tech demo at present, though I hope to have a build with some gameplay out by the end of the Demo Day.

It's written in Jai, Jon Blow's new language.  The engine is homebrew, but uses some libraries - Jai comes bundled with a bunch of modules, including one that I'm using for cross-platform window creation and setting up openGL contexts, text rendering, drawing primitives/sprites, etc.  The language's modules are very hackable, which is nice.

There's a lot of raw OpenGL in the code, especially for the fluid dynamics simulation and rendering, which is done by having two textures for the fluid sim state (one 'now' and one which is for the next time step), and having the fluid sim shader read from the first and render to the second texture before the texture handles get swapped.