Khazad-dûm Benchmark: Gandalf vs Balrog in animated SVG

Inspired by Simon Willison's pelican benchmark: instead of a static pelican on a bicycle, models must generate a self-contained animated SVG (SMIL/CSS, no JavaScript) of Gandalf duelling the Balrog on the Bridge of Khazad-dûm. Two prompt variants per model: minimal (one line) and constrained (scene + animation requirements). Open the raw SVG to see the animation live.

Prompt 1: minimal

Generate an animated SVG of Gandalf duelling the Balrog on the Bridge of Khazad-dûm.

Prompt 2: constrained

Generate a single self-contained animated SVG (SMIL or CSS animations, no JavaScript, no external resources) depicting Gandalf duelling the Balrog on the Bridge of Khazad-dûm.

The scene must include:
- A narrow stone bridge spanning a fiery chasm below
- Gandalf facing the Balrog, staff in one hand and sword in the other
- The Balrog with visible wings, horns, and a flaming aura

It must animate for at least two animation loops:
- Flickering flames and glowing light on the Balrog and in the chasm
- Gandalf's cloak and robe waving
- A subtle pulsing glow from Gandalf's staff
- Both figures shifting stance as if clashing

Constraints:
- Single <svg> code block only, no explanation
- Loop must be seamless (no jumps when the animation restarts)
- Include XML comments describing what each group represents