## Introduction

Follow_123 is a puzzle game in which the player tries to find a path through a grid. We saw a version of it (with the name "Journey Finder") in the i newspaper. Please see Figures 1 and 2, which show our two versions of the puzzle. The first version has vertices labelled 1, 2 or 3 and the path follows only orthogonal links. The correct path visits every vertex and follows the sequence 1,2,3,1,2,3,1,2,... The second has vertices labelled 1, 2, 3 or 4 and connections can also be made diagonally. The correct path visits all vertices and follows the sequence 1,2,3,4,1,2,3,4,1,2,... There are 1000 puzzles of each type, sorted on difficulty, easiest first.

### Contents

At the start of a game all possible links will be drawn using faint lines. These lines can be clicked on by the player to make connections between vertices: a left click adds a connection and a right click will remove one. The correct path links every vertex in the grid. For the 6x6 grid the path starts at the green vertex labelled 1 and ends on the green vertex labelled 4. For 8x8 the path runs from a green 1 to a green 1. Which 1 is the start and which the end is left for the player to work out.

The jigsaw shaped icon at the top left of the game window contains a configuration menu. The follow_123 icon to its right is used to change to a different puzzle: left click selects a random puzzle number, right click the next number in sequence. To the right is a wand icon which is used to request a hint. Right again is a thumb icon which will turn down if an error is detected. Next right, the sad smiley can be used to show the solution. The box to its right contains the current puzzle number and can be used to select puzzles. Next right is the puzzle difficulty score, and finally a clock which ticks every five seconds.

## Follow_123 Example 1

A partially complete follow_123 game of size 8x8 and using the vertex labels 1,2,3. Only orthogonal connections are allowed.

## Follow_123 Example 2

A partially complete follow_123 game of size 6x6 and using the vertex labels 1,2,3 and 4. Diagonal and orthogonal connections are allowed.

## Follow_123 Worked Example

The player uses the entry box at the top of the program window to enter the number of the puzzle to solve. She then looks to the corners, often good start points, and makes a bit of progress. After a few moves she clicks the thumb to check for errors. OK so far. But then she makes a mistake, and the next time the thumb is clicked errors are shown. A further click and they are removed. Each time an error is made she knows what not to connect. A bit later she requests a hint. The program highlights a 2 vertex in red. This vertex has possible connections to three vertices labelled 3, but of these, the vertex in the same column is only linked to a single 2 vertex, therefore it must be connected to the highlighted 2. She continues, making increasing use of the hint button.

## Playing

The program starts with a randomly selected puzzle displayed. All possible connections are shown by faint lines which respond to the mouse cursor: a left click adds a connection and a right click will remove one. There is only one "algorithm": find connections for which there is no other choice. At the start of the game there will be several, and as progress is made, the chosen connections will restrict other choices, thus making further progress possible.

If you click on the thumb icon the program will check for errors. If an incorrect connection is found, it, and all subsequent connections, will be treated as errors and highlighted in red. They can be removed individually with right mouse clicks, or more easily by a further click on the thumb icon. Frequent clicks on the thumb can avoid frustration. If our games did not employ the policy of treating all moves following an error as errors, puzzles could be solved by random clicking, followed by clicks on the thumb to remove any errors, but leaving the correct guesses. Where's the fun in that!

If you get stuck, a click on the wand will give a hint by highlighting, in red, a vertex for which the connection can be deduced. If you can work it out, click on the appropriate line; otherwise a further click on the wand will cause the correct connection to be made. If you ask for a hint when the grid contains errors the program will not provide a hint and will proceed as if you had pressed the thumb icon: errors will be highlighted and the thumb will turn down.

## Follow_123 Hint Example

The player has requested a hint which is shown by displaying the vertex in red. A hint vertex has a connection for which there is no other choice. It may be the hint vertex itself which has only one way to connect, or it may be that one of the vertices to which it is joined has no other choice. Here the 2 in the corner must be connected to the hint vertex.

## Follow_123 Error Example

A puzzle containing errors. The incorrect connection and all subsequent connections are highlighted in red; the thumb has turned down.

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# follow_123

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• 2024-07-13