What is the 15 Puzzle Game (by Dalmax) game, how does it work?

According to the introduction of Dalmax.Net, 15 Puzzle Game (by Dalmax) is a Puzzle game on the Android platform. There is currently a 1.7 version released on Mar 08, 2020, you can see the details below.

The classic 15-puzzle game (also called Gem Puzzle, Boss Puzzle, Game of Fifteen, Mystic Square and many others) is a sliding puzzle that consists of a frame of numbered square tiles in random order with one tile missing.

The object of the puzzle is to place the tiles in order (with the "hole" in the lower-right corner) by making sliding moves that use the empty space.

Version 2.1:
- Modify TIP help for showing advised move sequence
- Internal optimization for improving TIP computation