Okay, I can add a procedural galaxy effect to the background. This will involve creating a second shader program that draws a starfield and nebulae behind the rotating cube.

Here's how I'll approach it:

1. New Shaders for Galaxy: I'll write a new pair of vertex and fragment shaders. The vertex shader will be simple, just drawing a full-screen quad. The fragment shader will generate the galaxy effect using noise functions and pseudo-random star placements.
2. Separate Shader Program: These new shaders will be compiled and linked into a new WebGL program, distinct from the one used for the cube.
3. Render Order: In the main render loop, I'll first draw the full-screen quad using the galaxy shader program. Then, I'll clear the depth buffer and draw the cube using its original shader program on top. This ensures the galaxy is always in the background.
4. Uniforms: The galaxy shader will also receive u_resolution and u_time uniforms to make it dynamic and responsive.

Here's the updated code:

You're right, my apologies. I missed a crucial gl.useProgram() call for the galaxy shader program in the render loop. Without it, the GPU wouldn't know which shader to use for drawing the background, and the uniforms wouldn't be set for the correct program.

I've added the missing gl.useProgram(galaxyProg) call. This should now correctly render the galaxy background behind the cube.

Here's the corrected code: