Simple puzzle game inspired by Peg solitaire. Merge neighbor squares and left the last one on the marked destination.
There is an easy algorithm for generating levels - you just construct them backward.
The flaw of this game mechanic is that it is very hard to learn to find merging patterns that you know and to get better at the game. You practically have to think things through to the end before you even start merging anything. There is no room for error, recovery, or learning(=fun).