Distinguish glowing from dim. Then explore.

Each lantern belongs to a neighbourhood. Touch it and the lights beside it change too. A constellation emerges through these linked decisions, with as much thinking time as you want.

1. Distinguish glowing from dim

   Each lantern reports its current state. A dim square remains an active button, ready to change.

2. Imagine a plus sign

   A tap flips the chosen lantern and each neighbour sharing an edge. Off-board positions are ignored.

3. Try a reversible experiment

   Watch which lights change together. Undo light restores the previous board; repeating a tap also reverses that tap's effect.

4. Gather all sixteen

   The aim is a completely glowing grid. New constellation creates another solvable pattern and clears the tap history.