Four-nation artwork and emblems

The elemental_symbols.jpg sheet and air_nomads.png, water_tribe.png,
earth_kingdom.png, and fire_nation.png landscapes were supplied by the
site owner in the atla directory. Their original creator and licence
were not provided; no ownership or open-licence claim is made here.

The symbol sheet is unchanged. SVG clipping and luminance-to-alpha filters
isolate its four symbols and display them in the selected theme colour.
The landscapes are delivered as locally generated responsive WebP copies;
the source PNG files remain unchanged.

Combined toggle symbol — atla.png
Supplied by Saranga Mahanta, identified by him as AI-generated.
The supplied file is unchanged; CSS applies monochrome contrast and
blending to suppress its paper background, plus inversion in dark mode.

These assets replace the previously sourced Commons emblems and
hand-drawn SVG landscapes. The combined toggle replaces the earlier
DeviantArt artwork.

Unofficial fan tribute. Avatar: The Last Airbender and its nation designs
belong to their respective rights holders, including Nickelodeon.
No affiliation or endorsement is implied.