## DKM Towers Help

### Rules

Towers is a number puzzle where the cells in each row and column contain the numbers 1 to the grid size and no numbers are duplicated in any row or column. In addition, each number can be thought of as a tower of that height and the clue numbers around the grid tell you how many towers are visible from that direction. (Higher towers obsure lower ones after them.) So the sequence 2,1,4,3,5 would match a clue of 3 on the left, because the 1 is hidden behind the 2 and the 3 is hidden behind the 4. On the right, it would match a clue of 1 because the 5 hides everything else.
See the Walkthrough for an example of solving an easy puzzle.

### How To Play

• Click the "Menu" button, then select the "New Puzzle" menu item and select a grid size and difficulty level from the dropdown menu.
• Fill in blanks with the Pen (select a cell, then click on the number you want to enter).
• If you're not 100% sure of a number, you can make a note of it in the cell using the Pencil. To do this, click the "Pencil" icon to be placed in "Pencil mode".
• You may enter as many pencil marks as you like in each cell.
• To change back to "Pen" mode, click the "Pen" icon. You can also switch between pen and pencil modes quickly by pressing the "P" key or by using the mouse wheel. (See tips below.)

### Input Tips

#### Keyboard

If you prefer to use the keyboard rather than the mouse, you may:
• Use the arrow keys to navigate around the grid.
• Use the number keys to enter a number in the highlighted cell.
• Press the space or Delete key to remove any numbers from the highlighted cell.
• Press the "P" key to toggle between Pen and Pencil or use the mouse wheel (if not in Active Number mode - see below).
• Press the "U" key to undo last input.
• Press the "C" key to change all cells with one possible (pencil mark) to pen.
• Hold Shift key down to always enter in pencil (not operable with the number pad).

#### Other Tips

• Click the Undo icon (yellow arrow) to undo last input. You can undo all the way back to the beginning.
• Holding the Shift key when clicking on a number in the input panel will pencil that number in. You may find this more convenient than toggling between the Pen and Pencil icons.
• To remove just one pencilled number in a cell, enter that number again.
• To remove all pencil numbers in a cell, either click the eraser button or simply "pen" the final choice in.
• To remove all pencil marks from all cells, use the menu option under "Edit".
• There is an alternate mode of number input via the mouse called "Active Number Mode" (see below).

### Active Number Mode

If you select this mode (via Preferences menu option or icon), then the number you click from the Number Pad becomes the "active number". The mouse cursor will change to this number and clicking on any cell will enter it in that cell. This is the reverse of the "cell select" mode, where you highlight a cell and then select the number to input. Those that prefer to solve by focusing on one specific number at a time will find this mode more convenient.

To change the active number, select a new one from the Number Pad or scroll the mouse wheel down/up to increase/decrease the number. (If not in Active Number Mode, the mouse wheel will toggle between pen and pencil.)

In Active Number mode, all pencil functionality remains the same as does the ability to use the keyboard.

Here you select what grid size and the difficulty level. There are three difficulty levels, Easy, Medium and Hard.

One new puzzle for each grid size and difficulty is available each day.

Note: All puzzles have a unique solution and are solvable by pure logic - no guessing required!

##### Undo
Undoes the last input. You can undo right back to the beginning of the puzzle (unless you loaded a partially solved one). There is an Undo button which performs the same task, also the "U" key is a shortcut to this option.
##### Clear Possibles
This will clear all possibles displayed in the grid.
##### Clear All Input
This will clear all input (pen and pencil marks) displayed in the grid.
##### Pencil Marks to Pen
This option will convert all cells that have one pencil mark to a pen mark. The "C" key is a shortcut key for this option.
##### Save
Saves the current state of the puzzle to temporary user data on this computer. This is useful if you wish to come back another time to continue solving it.
Loads the last saved puzzle on this computer.
##### Print
This will print the puzzle at the state it is currently displayed in the grid.

#### Preferences

Here you may set various preferences. They are remembered and will reload from what was last set on that computer.

Active Number Mode: This toggles Active Number Mode, described above.

Show Pen/Pencil Cursor: Toggles whether the pen/pencil cursor is displayed over the grid or just the standard finger cursor. (Does not apply if Active Number Mode set as the cursor changes to the active number and will be gray if pencil mode.)

Auto Remove Pencil marks: If checked, when you enter a final (pen) number in a cell, that number will be automatically removed from the possibles in same group and adjacent cells.

Input Bar Position: You can choose whether to display the input numbers on the right or the bottom of the grid.

You can also customize the color of the grid and the numbers.

Main options to aid in solving puzzles.
##### Check Input
Checks to see if you have solved the puzzle correctly. Any errors made will be shown in red.
##### Hint
Suggests which cell may be the next easiest to solve. It will not fill in the value - for that you need to select the "Solve One Cell" option.
##### Solve One Cell
This is a very powerful option, especially as a learning tool. It will fill in one of the cells and displays the reason why that number is the answer to the cell. In the case where more than one step is involved, it will walk through the steps to solve the cell.
Note: Often there will be additional steps shown which are not necessary for the solving of that cell. This is because the computer algorithm goes through all cells looking to remove possible values using various strategies. For walkthrough, it will give you two options abbrev and full. Abbrev will remove any steps that do not include cells in the same row or column of the solved cell and in most cases is what you want. The "full" option is there in case a prior step not related to affected row or column may have an influence on an indirect cell that later will be pertinent to solving the final cell. It also serves as a useful tool for seeing how possible values can be eliminated.
##### Possibles Basic
This option will show you the possible numbers for each unsolved cell using the basic logic technique, ie it looks at what numbers are already present in the same row or column.
This option is very useful when you are solving a puzzle. It fills in the basic possibles and you can then work from there to eliminate other possibles.