This is a simple slide puzzle.

In all puzzles, there are stages for:
8-puzzle - 3x3 grid
15-puzzle - 4x4 grid
24-puzzle - 5x5 grid

You can start playing from any of these stages.

-- Worldview --
After the extinction of humanity, an explorer from outer space takes photos and contemplates this world.

By completing puzzles, you can collect pixel art illustrations of ruins. Additionally, reading the diary of the explorer who first witnessed these ruins allows you to delve deeper into this world.

Please give it a try.