Lucerna

Lucerna is an Akari puzzle — also published as Light Up — for players who like unhurried, honest logic.

You place lamps in the open cells. A lamp lights its own cell and everything in the four directions until a wall stops it. No lamp may light another lamp, every open cell has to end up lit, and a numbered wall has exactly that many lamps beside it.

Two rules pulling against each other

Lamps want to be everywhere, because every cell must be lit; lamps want to be nowhere, because no two may see each other. The numbered walls say where the balance lies, and reading them is most of the game.

Hints that explain

Stuck? The hint button shows a move and tells you which idea it used. On the hardest boards that idea is sometimes one step of look-ahead: try the opposite in a cell, and a few moves later the puzzle no longer works out.

Learn it by playing it

The walkthrough hands you real positions and asks for the one cell that follows, then shows you why. No board in it was made up — each is a genuine puzzle stopped at the moment the idea it teaches becomes the forced next move.

Measured in months, not streaks

Fill in every day of a calendar month and the month earns its own trophy. There is no streak to lose: a day you missed can still be filled in from the archive.

Built to be pleasant

Warm Material 3 design in light and dark, following your system colours. One tap places a lamp, and nothing counts down unless you asked it to. Lucerna is free to play and supported by respectful ads, which a single one-time purchase removes for good.