Zum is a free puzzle game developed by Charm for Android devices. The game's objective is to clear the board as quickly as possible by adding adjacent numbers to find the ZUM number, which is displayed at the top of the screen.

To play, you need to move the selection square by dragging or clicking to highlight one or more numbers along the edge of the board. The selected numbers are cleared when the last digit of the sum of the numbers is equal to the ZUM number. The more numbers you select, the more points you get. However, an incorrect selection will cost you a point.

Zum is a fun and challenging puzzle game that will keep you entertained for hours. With its simple gameplay and intuitive interface, it's easy to learn but difficult to master. If you're a fan of puzzle games, Zum is definitely worth checking out.