AKUNUR 2.10.3 — RING AND SECTOR DESIGN TEST

Purpose
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This build tests a more intuitive visual model for locating Echo positions:

  SAME RING → OPPOSITE ELEMENT → SAME OFFSET WITHIN THE SECTOR

The six sector pairs are:
  Wind ↔ Rock
  Rain ↔ Fire
  Sand ↔ Snow

Board appearance choices
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1. Standard board
2. Subtle ring shading
3. Ring shading + six sectors

The unsuccessful ring-boundary choices have been removed from the selector.

Implementation
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Every board cell now has a sector class and data attribute:
  sector-wind, sector-rain, sector-sand,
  sector-rock, sector-fire, sector-snow
  data-sector="..."

The sector build adds:
- very restrained tonal variation between wedges;
- a short dotted alignment mark beyond each board axis;
- an elemental symbol and label outside each sector.

Most future visual tuning can be performed in board-theme.css alone.
