Each round, a grid of similar glyphs appears. Exactly one differs (rotation, hue, or stroke width). Select the odd one before time runs out. Tiers raise difficulty by shrinking the difference and the time budget. Finish N rounds to complete a session.

• Mouse: click a tile.
• Keyboard: arrow keys to move focus; Enter or Space to select.
• Screen reader: each tile announces its position. Use standard grid navigation.