What the game is

Akari — "light" in Japanese, Light Up to the puzzle world — is Nikoli's 2001 puzzle about illumination as logic. A square grid mixes open cells with black walls, and some walls wear a number. You place bulbs on open cells; each floods its row and column with light until a wall cuts the beam dead. The target is total brightness — every free cell lit — under one strict courtesy: no two bulbs may shine into each other's eyes. Numbered walls are the local tax: a wall marked 3 wants exactly three bulbs pressed against its sides.

What makes Akari different is that its reasoning runs along lines of sight: you watch corridors of light and ask who can see whom. The app's boards keep sightlines long — walls cover roughly a sixth of the grid and never touch each other edge to edge — and each puzzle is lit into existence first: a single generator pass drops a bulb on every cell still in the dark, guaranteeing a conflict-free reference solution. The win check grades the rules, not the reference: any final layout that lights everything cleanly wins.

How to play

The rules, in the order the in-game help sheet numbers them:

  1. The grid contains free cells and black wall cells.
  2. Some walls carry a number from 0 to 4.
  3. A bulb sits on a free cell and lights its own cell plus every free cell in the four directions until a wall blocks the light.
  4. Every free cell must be illuminated by at least one bulb.
  5. No bulb may be lit by another — two bulbs sharing a row or column with no wall between are forbidden.
  6. A numbered wall must have exactly that many bulbs in its orthogonally adjacent cells.
  7. An unnumbered wall tolerates any number of adjacent bulbs, including zero.

Step by step. Medium is an 8×8 grid — the HUD names the level; scattered gray walls, some of them numbered, everything else dark.

Fresh medium 8×8 Akari: scattered gray walls, four of them numbered (2, 1, 0 and 1), and every free cell empty of bulbs and light.

One tap, one bulb: touching a free cell lights it; touching the same cell again takes the bulb back out — the whole game is a toggle, and walls simply ignore your finger. A warm tint floods each bulb's row and column up to the first wall, so coverage and dark spots read at a glance. Conflicts flash red: bulbs that can see each other, walls overshooting their count. A wall with too few stays quiet — unfinished, not wrong. Six hints per game, each dropping a reference-solution bulb through the same toggle the player uses; every placement stays undoable.

Mid-game 8×8 Akari: six amber bulbs whose rows and columns glow warm light up to the first wall, the rest of the board still dark.

The pause menu is the same bench as everywhere else in the catalog — Resume, Restart, New Game, How to Play, Difficulty, Settings and Statistics, seven options in the browser build; the installed app adds Quit — and the help sheet holds the seven rules.

Akari pause menu (Paused), its eight options in two columns over the half-lit board dimmed by the scrim.

In-game Akari (Light Up) help sheet: bulb-and-wall description plus seven numbered rules on line of sight and wall counts, with a Close button.

The win arrives when darkness stops existing: every free cell lit, no mutual glare, each numbered wall touched by exactly its count. The panel reports time and hints spent — ten bulbs were enough for this 8×8.

Solved 8×8 Akari: ten bulbs light every free cell without seeing each other, numbered walls satisfied, behind the "You win!" panel with confetti.

Strategy and tips

  • Start with 0s and the fat numbers. A 0 wall poisons all its open neighbours; a 4 needs bulbs on all four sides, and a 3 in a corner has its answer forced. Free placements first.
  • Finish half-done walls. A numbered wall seeing N−1 of its N bulbs with one legal neighbour left is decided — place or eliminate, immediately.
  • Pair up look-alikes. Two open cells that see each other can hold at most one bulb between them; for a cell lit from only one corridor, mutual exclusion often leaves exactly one place for the bulb.
  • Never orphan a shadow. Before committing a bulb, check what it still leaves unilluminatable — a cell no legal bulb can reach has lost you the board.

Controls

  • Mouse and touch: tap a free cell to toggle its bulb; buttons for Undo, Hint, New Game and the pause menu.
  • Gamepad: the D-pad walks the cursor cell to cell — walls are not navigable stops, it simply skips them — A toggles the highlighted free cell, Start opens and closes the pause menu, and B steps back: it closes menus and panels, and with the cursor already on the board it asks whether you want to quit.
  • Keyboard: arrow keys move the same cursor and Enter performs the tap.
  • Undo walks placements and removals back one at a time — hints included. Restart replays the same wall layout dark; New Game rolls a fresh one, and changing difficulty discards the run in progress.

Difficulties and variants

Akari scales the grid, never the rules: Easy is 7×7, Medium 8×8, Hard 9×9 and Expert 10×10, with the same six hints at every level. Bigger boards mean longer corridors to audit; the deduction stays the same, the bookkeeping stretches. About half the walls carry numbers, and a clue never exceeds the four sides a wall can face.

Where to play

Akari is free in the Tab and Blank catalog, in the browser, nothing to install: play Akari.

If counting neighbours against numbered squares was your medicine, the same logic shelf keeps Creek — its intersections tally shaded neighbours the way Akari's walls tally bulbs.