Killer Sudoku is also known as Sum Sudoku, which is a type of puzzle game that combines the features of KaKuro and Sudoku.

Just like any other Sudoku, the columns, rows, and three by three blocks consist of numbers 1 to 9. 

Also, the dotted lines represent areas known as cages that contain a series of digits (non-repeated). When you sum up the numbers present in a cage, you will attain the sum displayed in the clue. 

History

• Killer Sudoku puzzles originated in Japan in the mid-1990s, and earlier, they were termed as “samunamupure.” The name – Killer Sudoku was given to the game for most English speaking countries. 
• In usual Sudoku puzzles, when you look at the grid layout, it is somewhat symmetrical around the horizontal, vertical axis and diagonal axis, or you can quarter/half-turn towards the center. 
• Killer Sudoku needs the player to have solver skills at mental math, and the most difficult ones take hours together to solve. So, you need to be sharp with mental arithmetic to stay in the game and solve the puzzles.

Goal 

• The goal of the game is to fill in the grid using numbers from 1 to 9 in a fashion that the below-mentioned rules are followed 
• Every row, column & and no net consists of every number precisely once
• The addition of all the amounts present in the cage should match the small number displayed in the corner.
• In the cage, every number appears just once means they are not repeated. It is a standard rule of Killer Sudoku, which signifies that every pen can have nine cells only.
• In this game, – ‘Killer X,’ is an added rule wherein every lengthy diagonal consists of each number just once. You need to follow the regulations and have excellent math skills to solve these puzzles.