How to Solve It

1. The two-minute version

Each cell has four numbers: its cube (the buttons under the board), its floor (height), its row and its column. You place one cat per colored region, and:

• One cat per cube, per floor, per row and per column. On a 4⁴ board that's 4 cats, and each cube, floor, row and column gets exactly one.
• Cats can't touch, not even diagonally or across neighboring cubes.
• Let the app do the bookkeeping. With assist on (the eye), every cell your cats rule out fades away, and cells that touch a cat in the next cube turn red. You only ever think about the bright cells.
• Look at one floor at a time. Tap a floor number to look straight down on it, like a flat puzzle.

The whole game is one question, asked over and over: "where can this region's cat still go?" Start with the smallest region. When there's only one place left, that's the cat.

2. How to read the pictures

The game shows one cube at a time in 3D. Here every cube is laid out flat instead: each column is a cube, each row is a floor (top floor first), and each little grid is that floor seen from above. This is the real Level 1, a small 3⁴ board with three cats to find.

• Solid outline: the cells the step is about.
• Dashed outline: what the step changes (a cat, or ✕s).
• Faded cells are not part of the step.

3. Level 1, solved step by step

These are the exact hints the game gives, in order. Try each one in the app as you read.

1. Step 1 · Confinement

   Every cell the teal region has left is in floor 3. Floor 3 only gets one cat, so it has to be the teal region's. That rules out the other 17 open cells in floor 3.

2. Step 2 · Last cell standing

   The lavender region needs exactly one cat, and every other cell in it is already ruled out. Only one cell is left, so the cat goes there.

3. Step 3 · Confinement

   Every cell the teal region has left is in cube 3. Cube 3 only gets one cat, so it has to be the teal region's. That rules out the other 4 open cells in cube 3.

4. Step 4 · Last cell standing

   Column 2 needs exactly one cat, and every other cell in it is already ruled out. Only one cell is left, so the cat goes there.

5. Step 5 · Last cell standing

   The sage region needs exactly one cat, and every other cell in it is already ruled out. Only one cell is left, so the cat goes there.

4. The three moves

Last cell standing

A region, cube, floor, row or column has only one bright cell left. That's the cat. Tiny regions of a single cell are free cats: grab them first.

Confinement

All the bright cells of a region sit on one floor (or in one cube, row or column). That floor's one cat must belong to the region, so every other cell on that floor is ✕. It works the other way round too: if all of a cube's bright cells belong to one region, the rest of that region is ✕.

What if?

Only on medium puzzles and up. Imagine a cat in a cell. If it would fade out every bright cell of some region, that cell can't be a cat. Good cells to test are the ones right next to a small region.

Two cats can only touch if they're one step apart in every direction at once: next cube, next floor, next row and next column. That's why red cells only ever show up in the cubes on either side of a cat.

5. When you're stuck

1. Turn assist on, so only the bright cells are left to think about.
2. Find the smallest region. Count its bright cells. One left? Cat.
3. Are all of its bright cells on one floor, or in one cube? Clear the rest of that floor or cube.
4. Check each cube button: a cube with one bright cell left has found its cat.
5. Still nothing? Tap the bulb. Hints point you to the right place first, and only explain if you ask.