Traffic Lights
Another deceptively straightforward puzzle that works well onscreen. Click or tap a square and all those on the same row
and column (except the one you tap) change. The twist is that there are four different squares which appear in turn.
You may recognise these as UK traffic lights.
Red is STOP, the red and amber appear together to tell you that the lights are about to change to green, and green is GO. Then amber alone says they are about to change back to red, and red is STOP.
Your aim is simply to turn all the traffic lights to GO. The emergency Solution button is there for if you are really stumped. The information appears further down the page.
Red is STOP, the red and amber appear together to tell you that the lights are about to change to green, and green is GO. Then amber alone says they are about to change back to red, and red is STOP.
Your aim is simply to turn all the traffic lights to GO. The emergency Solution button is there for if you are really stumped. The information appears further down the page.
Hint:
The puzzles take 4, 5 and 6 moves in turn to solve.Making a Puzzle
The trick to making a puzzle is to work backwards. Start off with the all-green board above and click or tap three times on each square you choose (keeping a note of the number of each square). Then the solution will be to tap the same squares, in any order, once each. So to set up a puzzle solved by tapping squares 8, 20 and 12, just tap three times on 8, 20 and 12. To solve, click once on 8, 12 and 20. Knowing the numbers, you can easily set up the puzzle again for your friends to try.Solution
Numbering the squares across and down from 1 (top left) to 25 (bottom right), the answers are:
Solving a Puzzle
The principle of solving these puzzles is a bit heavy but it works. Draw a series of 5 x 5 boards. Fill in the first with the number of clicks it takes for each square to be turned to green. Then mark each row and column with the maximum number of clicks it needs to get it to 0. The Hard puzzle looks like this:
Now assuming we don’t click on 3 as this would hold the number but click on squares which will reduce the 3’s to 2’s let’s start top right to reduce the top row. After the click it looks like this:
Then three more logical squares. After each is chosen this is the result:
We are left with only two rows and columns to reduce and these can be zeroed with the two squares shown. The last diagram shows the six squares in blue that we have discovered will solve the Hard puzzle.
Numbering the squares across and down from 1 (top left) to 25 (bottom right), the answers are:
Easy Puzzle — 7, 9, 17, 19
Medium Puzzle — 21, 10, 4, 15, 17
Hard Puzzle — 2, 19, 15, 17, 13, 5
Medium Puzzle — 21, 10, 4, 15, 17
Hard Puzzle — 2, 19, 15, 17, 13, 5
Solving a Puzzle
The principle of solving these puzzles is a bit heavy but it works. Draw a series of 5 x 5 boards. Fill in the first with the number of clicks it takes for each square to be turned to green. Then mark each row and column with the maximum number of clicks it needs to get it to 0. The Hard puzzle looks like this:
Now assuming we don’t click on 3 as this would hold the number but click on squares which will reduce the 3’s to 2’s let’s start top right to reduce the top row. After the click it looks like this:
Then three more logical squares. After each is chosen this is the result:
We are left with only two rows and columns to reduce and these can be zeroed with the two squares shown. The last diagram shows the six squares in blue that we have discovered will solve the Hard puzzle.
