The app is for the mathematical puzzle known as KenKen or Keisan-Block (in Japanese).
Fill all the colorful cells with integers from 1 to 4 so that:
- in each row/column, every integer appears exactly once, and
- in each block (same colored cells), the calculation (+, x, - or %) equals to the small number.
We have four levels from 4x4 to 7x7, each of which contains 30 puzzles. Have fun!