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How to Play

A Corner Place puzzle is a 5x5 grid of squares, which are each divided into 4 quadrants. The goal is to fill one number from 1-5 into each quadrant of each square while obeying three rules:

  1. Each number must appear in each quadrant exactly once in each column.
  2. Each number must appear in each quadrant exactly once in each row.
  3. No two squares can share two quadrant numbers in common.

In the example below, we have two squares that both have 1 in their northwest corner and both have 4 in their southeast corner.

In order to place a number into the grid, you simply press on the quadrant of square you want to fill, then press the appropriate number button that appears. For example, here, we fill in a 2 into a space in the grid:

(If you are playing on PC, you also have the option of pressing the corresponding numeric key on your keyboard.)

If you fill in a value incorrectly, you can remove it by simply pressing the same number again (On PC, you can also use the Delete or Backspace keys to clear a value.)

Visual Aids

There are a few visual aids that have been added to the game to help you track the constraints based on quadrants within a row and based on pairs of quadrants.

As you can see from some of the other examples, each quadrant uses a distinctive font. This should make it easier to tell at a glance what quadrant a number is in.

To aid in identifying the elements of a single quadrant across a row or column, the game automatically highlights the shared quadrants of every square in the same row or column whenever you mouse over or press down on a quadrant of a square.

You can also see that when hovering directly over an already-filled number, that number gets highlihgted in blue, and all instances of the same number in the same quadrant are highlighted in blue. This can help in determining whether or not that number has been

For cross-referencing quadrant pairs across different squares an extra "press-and-hold" feature was introduced. This feature can be activated by pressing on a quadrant and then dragging to another quadrant in the same square.

As you can see, every square that shares the same value in the quadrant you dragged to gets highlighted-- both the shared value (in blue), and the quadrant corresponding to the one that you initially pressed down on (in green, like the rows and columns). This makes it easy to get a visual read on what squares can cause a conflict. In this example, 1, 2 and 5 are in the same row or column, and the press-and-drag feature reveals a 3 that has already been paired with the northeast 1, meaning that 4 is the only valid option remaining.

Tips

Although there are only three explicit rules of the puzzle, it's possible to derive additional rules of thumb that can be used as deduction shortcuts.

  • A quadrant of a square must not be filled with a number if:
    • The number already appears in the same quadrant in the same row or column.
    • Doing so would create a pair of numbers in two quadrants that already appear together in the same quadrants of another square.
    Cross-referencing these two rules can reveal required placements through process of elimination.
  • A quadrant of a square must be filled with a number if:
    • The square is the only square missing that quadrant in its row or column in the row, and that number is the only unused number for that quadrant in the row or column.
    • That number has already appeared in that quadrant of other squares 4 other times, and this is the only square that doesn't lie in the same row or column as the other instances.
  • Some special case scenarios:
    • If a number has already appeared in a particular quadrant three times, then this narrows it down to only four possible locations for the last two instances, and these four locations will lie at the corners of a rectangle. If one of those four locations is already occupied, the two remaining instances must be the two locations that share a row and a column respectively with the occupied space.

This is not a full list of deduction shortcuts and you may discover additional shortcuts on your own, but these cover most of the basic cases that you'll encounter.