Puzzle games to play while waiting in line or on hold

The clerk scans each bottle slowly while the person ahead at the pharmacy counter has a long order. Others in line shift their weight and look at their phones. Someone with a small grid open has one job: fill the empty cells so that each row, column and box holds each number once. The grid is 4x4, so it uses the numbers 1 to 4 and has four boxes of four cells each. During a still moment in line, the solver looks at one row for a cell where only one number fits. When the line moves forward, the solver stops after placing the current number, puts the phone in a pocket and steps ahead. The grid stays as it was, with every filled cell in place.

Choosing a board that ends quickly

A 4x4 grid has 16 cells, and a 6x6 grid has 36, so the smaller board usually finishes within a short wait. The standard 9x9 grid has 81 cells. It first appeared in the May 1979 issue of Dell Pencil Puzzles & Word Games, with nine 3x3 boxes, and a full board of that size often takes longer than a pharmacy line or a hold queue allows.

Solvers who wait often choose a size based on how many minutes they expect to have. A wait of two or three minutes fits the 4x4 board. If the wait may run long with no clear end, the 6x6 board may fit, since the solver can stop at any placed number and come back later.

Before starting, players tend to look at the board for a few seconds. Players count the filled cells first, since a board with more given numbers leaves fewer cells to fill. Players also check for any row, column or box that is nearly full, since one missing number there can go in right away. When no such spot shows, many players pick a smaller board rather than start a large one they cannot finish.

Stopping in the middle of a level

Many solvers mark the last cell they filled when the line moves, before they put the phone away. On paper, the mark can be a small dot in the corner of the cell. On a screen, remembering the row and column of the final number is usually enough. When the wait ends, they read that number again and confirm it does not repeat in its row, column or box before placing the next one.

Each number falls to the lowest empty cell of the column it is dropped into, so a drop puzzle keeps its order. If the screen locks or the board becomes lost or unclear, a solver who wrote the drops on paper can replay them in the same order. A short note like "3 in column 2, then 1 in column 4" is enough. The board comes back the same way when the first drop goes in first.

Timed levels keep running while the phone is in a pocket, so a long or uncertain wait often fits an untimed puzzle or a paper grid better. In NumFall, levels are timed and a fast finish with no mistakes earns 3 stars, so solvers who want a quick level for a short line can find NumFall on the App Store.

Playing one-handed on a phone

Many solvers hold the phone in one hand, with the lower edge resting against the palm and the thumb free to move across the screen. The thumb taps a column to drop the chosen number. Columns on the far side are the hardest to reach, so players with smaller hands often tilt the phone toward the thumb or slide the grip lower on the back.

Solvers keep the number tray within thumb reach by holding the phone the same way each time, since the tray sits below the grid. Picking a number and tapping a column take two taps in a row, and a steady grip means fewer drops land in the wrong column. At a counter, the other hand is usually busy with a bag, a card or a prescription slip.

The App Store listing for the drop puzzle described above lists iPhone and iPad with iOS 17 or later, and says the download is free with no ads.

Some solvers test their grip once before they join a line. To test, they pick any number, tap the column farthest from the thumb, and check whether the phone stayed steady in the palm.

NumFall is made by the publisher of this site. Any health or brain-training points here are general information, not medical advice.