"Siji" is a word of "One" in Japanese.
This is a logic game, once played in ancient Asia with stone rocks.
In the start of each game, they are arranged on the playing field, often displaying particular figure or pattern. The player would take away rock after rock from the ground, following particular rule, until only one remains.
The rule is that a rock can be taken out only if it is "jumped over" by another one, which was placed next to it (east, west, north or south) and is moved to a free palce on the board.
Try a few times and you may find yourself carried away in the ancient thrill of a simple game with many combinations.
Levels are arranged in increasing difficulty order, but are not required to be played one after another. Feel free to jump back and forth and enjoy the wonderful game of one the best you can...