Nice! Odin looks cool.
Is that an alternative to OpenGL?
Not really. OpenGL is a graphics API, for more or less giving flat instructions to the graphics card. SDL, however, includes a 2-D renderer out of the box which is very easy to use: You can load in a bitmap, send it to a texture and then draw it to the screen. I don’t know if the Odin binding of SDL binds the renderer API, but chances are it does. Here’s an example of drawing a picture with SDL’s renderer.