You have a square grid; each square may contain a character from A (or 1) to a given maximum. Your objective is to put characters in some of the squares, so each character appears exactly once in each row and column.
The rules vary depending on the game mode:
Number Ball was invented by Inaba Naoki. The original puzzles are available here: http://www.janko.at/Raetsel/Nanbaboru/index.htm
The designer of ABC End View is unknown.
Salad uses a control scheme similar to Solo, but with the ability to mark empty squares.
Left-click to select a cell, then type a letter or number on your keyboard to enter it. Press Backspace or Space to clear a cell.
Press ‘X’ to mark a cell as empty, or press ‘O’ to mark a cell as “definitely not empty”.
Right-click a cell, then type a letter or number to add a pencil mark. Pencil marks can be used for any purpose. The letter ‘X’ can also be used to indicate a cell that might be empty. A preference makes right-click switch on a sticky pencil mode instead, which stays on until you right-click again.
You can also use the arrow keys to move the selected cell around. Press Enter to toggle between entering letters/numbers and entering pencil marks.
Press the ‘M’ key to fill every empty cell with all possible pencil marks.
These parameters are available from the ‘Custom…’ option on the ‘Type’ menu.