Number puzzles with large grids on iPad
Number puzzle games for iPad with large grids: learn a row, column and box scan for 6x6 and 9x9 boards.
On a 9×9 board on an iPad, one column is half filled, with the top four cells holding numbers and the lower five still empty. The solver focuses on the lowest empty cell and asks which number can fit there. The solver first checks the row that holds the cell, then the column, then the 3×3 box around it, crossing off every number already present.
On a large grid, there are more cells to scan, and an error has more places to hide. A wrong number placed early may not show itself till several rows later.
Each row, column and box must hold each number once. In NumFall, the order of drops decides the board, since numbers fall to the lowest empty cell of whichever column the solver taps. A number that fits the lowest cell right now may block another number from the cell above it.
Why a 9×9 board asks for more scanning
Before placing any number on an 81-cell board, a solver usually checks three units: the row, the column and the 3×3 box that contains the target cell. A given cell belongs to all three units, and each unit holds nine cells, so one cell can rule out as many as twenty other numbers. Solvers who read the units in the same order every time tend to catch conflicts that a quick glance would miss.
Bigger boards came later than smaller ones. The New York Times printed its first puzzles of this type on February 8, 2009, a 4×4 grid and a 6×6 grid, and the 9×9 size is a later step up in the amount of scanning.
In a falling-number game, a value placed early fills the lowest empty cell of a column. That cell is then taken, and the next number dropped in that column lands one cell higher. A value placed early can leave a later number with no legal cell in that column.
Skipping one unit is a common mistake for beginners. Checking the row and the column, a solver sees that a 7 fits and drops it without reading the box. The conflict appears only once more numbers have fallen on top of it.
Reading a large board on an iPad screen
An iPad gives the grid and the number tray more room on the screen at once. A solver can keep the full 9×9 board and the tray in view while running down a column, so there is no need to scroll or to remember which numbers are still available. The column check becomes a matter of looking at the nine cells, then at the tray and then at the lowest empty cell.
On a large board, pencil notes work best when they stay short. A note written several moves ago may list a number that can no longer go there, because each placement changes the rows, columns and boxes around it. Many solvers keep notes only for cells with two candidates, and they clear a note as soon as a drop makes it doubtful. A cell with six small numbers written in it usually has to be rechecked from the start.
The game these solvers play supports Dynamic Type, VoiceOver and Reduce Motion. A solver with low vision can raise the text size in the iPad settings, or use VoiceOver to have the screen read aloud. A solver who is sensitive to motion can turn on Reduce Motion to cut down on movement on screen.
Choosing a first large board to practice
Solvers who want to practice on a large board can start with the Classic 6×6 set, which has 100 levels. Each row holds six cells, so a solver can read a full row in order, left to right, and check every number against the column and the box before dropping anything. Once that reading comes without skipped cells, the Master 9×9 set is the next step, also with 100 levels.
Levels are timed, and finishing fast with no mistakes earns 3 stars. A solver who wants to learn the scan first may ignore the clock and work slowly, since a slow finish still completes the level. Star counts can be raised later, after the row, column and box checks have become routine.
Each player gets the same puzzle, as The Daily Drop offers one puzzle per day. A short session on a 9×9 board suits it, since a solver can compare notes with other people who worked the identical grid.
NumFall is free on iPhone and iPad with no ads, no accounts and no purchases, and NumFall on the App Store lists it as requiring iPadOS 17 or later.
A simple practice step: pick one row on a 6×6 board and check each cell in it, crossing off the numbers already present. Repeat the same scan on a 9×9 board before starting a timed level.
FAQ
How do I check a 9x9 number puzzle on an iPad without missing a conflict?
Read the row of the lowest empty cell in the column first, then its column, then the 3x3 box it sits in. A wrong drop stays hidden until later unless each number already present in those three units is crossed off.
Why do I keep making mistakes on big number grids?
Skipping one of the three units, like checking the row and column but not the box, is a common beginner error. A wrong number placed early can stay out of sight for several rows, so the mistake may be hard to trace.
Should I start with a 6x6 board before trying a 9x9 number puzzle?
Many people start on a 6x6 board, since each row holds six cells that can be read in order. After the scan comes out without skipped cells, the larger 9x9 board is a natural next step.
Can I use pencil notes on a large number grid on iPad?
Short notes work best, since each placement changes the rows, columns and boxes around it. Clearing notes as soon as a drop makes them doubtful keeps the board accurate.
Sources
NumFall is made by the publisher of this site. Any health or brain-training points here are general information, not medical advice.