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## How to play

This is an example of a finished Towers puzzle. This puzzle borrows heavily from Sudoku puzzles, but also has some of it's own rules. Firstly, this is a 9x9 grid, so each row and column must contain the number 1-9 once and only once. If you have a 5x5 grid, then each row/column would have to contain the numbers 1-5.
A Towers puzzle also has clues on both sides, and top/bottom. The clues tell you how many 'towers' you can see if you were look from that point in to the puzzle. The number in each cell tells you the height of that tower. As an example, take the top row looking from the left, we have a clue of '4'. Looking in to the puzzle from that point we would see 1, 3, 7, 9 (i.e. four numbers/towers). The 2, 5, 8, 4, 6 would be hidden behind the higher numbers/towers before.
Take the left-most column from the top, we have to clue '5'. So, looking down that column we would be able to see 1, 2, 5, 8, 9 (i.e. 5 numbers/towers). The 7, 6, 3 and 4 would be obscured behind the higher numbers/towers before.
This is an example starting grid. The easiest place to start is with the '1' clues. This clue means you can only 'see' one tower from that side, the only way this can happen is if the first number is 7 (in this case the width/height of the grid, i.e. the highest number).
Because each row/column will have one '7' in it, you will always have 4 clues of the value '1'. It's a little unfortunate in this case that it has only given us 3 numbers we can enter, and not the full 4.
After this easy start, you normally have to resort to applying the rules and entering pencil marks. However, for this particular puzzle we can enter another number immediately.
Look at the row with the highlighted cell. We are looking for where to put the 6'. It can't go to the right of the '5' because that would leave a number lower than 5 to the left of the 5, and we wouldn't be able to satisfy the '3' clue on the left. The '6' can't go in the left-most cell because then that would give us a clue of '2' on the left, so it must go in the highlighted cell.
Look at the right-most column, the hilighted cell in particular. The clue at the bottom is a '2', so the highlighted cell must hide the two cells above it. Taking in to account the 5 in the row already, and the '1' in the column already, that cell must 6 or 4. It can't be a 3 because that would mean the two cells above would be a combination of 1 and 2, and we already have a 1 in that column.
We inspect interesting parts of the puzzle inserting pencil marks as we go until we are able to start inserting numbers. As the puzzle starts to fill, we can start applying more of the traiditional Sudoku techniques.
This page will automatically load the Towers Puzzle for today. If you want to play a different puzzle, go to the archive page and choose your puzzle.
There are two ways to play a Sudoku puzzle, you can just use the mouse/touchscreen, or you can use the mouse and keyboard. You can switch between the two methods any time you like, and can use a combination of both.

### Playing with a mouse/touchscreen.

• When you have found a square where you can enter a number, click/touch that square. The square will turn light blue.
Above and below the puzzle is the number selection. Click/touch the number you want to enter in to that cell. If there is already a number in that square, it will be over-written.
• If you want to enter a pencil mark, click/touch the square you want to put in a pencil mark. It will turn light blue. Click/touch the pencil icon above or below the puzzle. This icon will turn light blue, and you are now in pencil marks mode.
Whenever you click/touch a number now, a pencil mark will be put in the square instead. To remove a number as a pencil mark, make sure you are in pencil marks mode, and click/touch the number again.
You can exit pencil mark mode by clicking/touching the pencil icon, it will turn back to normal.
• If you want to clear a particular square, make sure that square is selected and is in light blue. Click/touch the eraser icon. If there is a number in that square, it will be removed. If you click/touch it again, any pencil marks in that square will be removed.

### Playing with a mouse and keyboard.

• You will need to select a square by clicking on it with the mouse, it will turn light blue. You can change the current square by using the cursor keys on your keyboard.
• To enter a number, press that number on the keyboard. If there is already a number in that square, it will be overwritten. To remove a number, press the backspace or delete key on your keyboard.
• To enter a pencil mark, press control, shift, or alt on your keyboard at the same time as pressing a number key. Do the same thing again to remove that pencil mark.
Any mistakes you make will be hilighted in red. The website will know when you have completed a puzzle and will tell you. If you have an account and are logged in, the website will remember that you have completed that puzzle. You will also take part in out leaderboards. It's free to create an account!