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Checkerboard Bridge (Chequerboard Bridge in the UK version) is a puzzle in Professor Layton and the Unwound Future.

## Puzzle

US Version

The bridge below has been painted in a black-and-white checkerboard pattern.

Starting at the bottom-left arrow, you need to cross the bridge and finish at the upper-right arrow. You can move one square at a time, either up, down, left, or right. You can't move diagonally.

Now here's the tricky part: how many different routes across are there that touch exactly four black squares and three white squares?

UK Version

The bridge below has been painted in a black-and-white check pattern.

Starting from the bottom-left arrow, you need to cross the bridge and finish at the top-right arrow. You can move one square at a time, either up, down, left or right. You can't move diagonally.

Now here's the tricky part: how many different routes across are there that cross exactly four black squares and three white squares?

## Hints

Click a Tab to reveal the Hint.

US Version

Your task is to find all the routes that meet the conditions.

Touching four black squares and three white ones means you have to cross the bridge in seven moves, so you can't afford to backtrack.

UK Version

Your task is to find all the routes that meet the conditions. Think about how each route crosses the central column of squares on the bridge.

Crossing four black squares and three white ones means you have to cross the bridge in seven moves, so you can't afford to backtrack.

US Version

Once you've figured out the types of routes that will work, just go ahead and count them up one by one.

As Hint One mentioned, backtracking won't work. If you keep the other conditions in mind, you should be fine.

UK Version

Once you've worked out the pattern in the routes that work, just go ahead and count them one by one.

As Hint 1 mentioned, backtracking won't work. Keep the other conditions in mind and you should be fine.

US Version

One route is to go straight all the way to the top row and turn right.

Another is to go straight to the second row from the top, turn right, and then turn left again at the right column.

These are just two of several different possibilities. Count each one!

UK Version

One route is to go straight up the top row and then turn right.

Another is to go straight to the second row from the top, turn right, and then head up again when you reach the rightmost column.

These are just two of several different possibilities. Count each one!

US Version

There are more than 10 routes, but less than 20.

Keep on counting! Or...start guessing!

UK Version

There are more than 10 routes, but fewer than 20.

Keep on counting!

## Solution

### Incorrect

US Version

You can move vertically and horizontally but not diagonally.

Count the routes again.

UK Version

You can move vertically and horizontally, but not diagonally.

Count the routes again.

### Correct

Precisely!

US Version

There are 15 different routes. More than you'd think, huh?

UK Version

There are 15 different routes. More than you'd think, eh?

A big thanks to http://professorlayton3walkthrough.blogspot.com

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