Why does the Mandelbrot go black and featureless when I zoom in?
You have run out of iterations. Deep in the set's boundary, points take many more iterations to escape, and any point that has not escaped by the cap is painted as interior black. Raise the iterations slider toward 500 and the structure comes back. This is the single most common misunderstanding about zooming into fractals.
What is the difference between the Mandelbrot and the Julia set?
Both iterate z = z^2 + c. For the Mandelbrot, c is the pixel's coordinate and z starts at 0. For a Julia set, c is a fixed constant and z starts at the pixel's coordinate. So there is one Mandelbrot set, and a different Julia set for every value of c. The Mandelbrot is effectively a map of which c values give connected Julia sets.
Why can I only zoom to 40x?
Because the math runs in double-precision floating point, and beyond a certain zoom the pixel spacing falls below what a double can represent, so the image degrades into blocky artefacts. Deep zooms into the Mandelbrot need arbitrary-precision arithmetic and perturbation techniques, which are far heavier than a per-pixel loop on the main thread.
Why is the recursion depth capped at 8?
Because the work grows exponentially. Sierpinski triples its triangle count each level (3^8 = 6561 at depth 8) and Koch quadruples its segments (4^8 = 65,536 per side). Depth 12 would be thousands of times more work for detail finer than a pixel.
Can I use the download as wallpaper or print it?
The PNG is exactly 640 x 640, which is fine for a small web image but too small for a phone wallpaper at native resolution, and well short of print. There is no higher-resolution export.
What does the base hue slider actually do?
It rotates the starting point of the color ramp. The hue for each pixel is the base hue plus 300 degrees times the fraction of the iteration budget the point survived, so moving the base hue shifts the whole banding pattern around the color wheel without changing the underlying math.