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Foundational

Grid logic

Switch lights on and off until the clues leave you only one possible board.

5 lessons30 exercises49 min
Understanding0%

What you will learn

  • Turn a written clue into an exact constraint on a grid
  • Combine counting, comparison and exclusion clues until one board remains
  • Plan a sequence of switch presses when one press changes several lights
  • Use even and odd counts as a shortcut and as a proof of impossibility

Lessons

Stage 1 / 5

  1. Toggles

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    Switch bulbs on and off until every clue holds at the same time.

    0/6 exercises · 6 required · 8 min

    Start

  2. Cascading lights

    One press moves several lights at once. Plan the presses, not the lights.

    Complete the previous lesson

    Locked

  3. Patterns of lights

    A single sentence can describe a whole board. Build the board it describes.

    Complete the previous lesson

    Locked

  4. Using parity

    Even and odd counts decide questions that counting one by one never could.

    Complete the previous lesson

    Locked

  5. Rows and columns

    Totals along both axes pin a board down faster than any single clue.

    Complete the previous lesson

    Locked