Carrying is Hard: Exploring the Gap between Hardness for NP and PSPACE for the Hanano and Jelly no Puzzles

TL;DR

This paper investigates the computational complexity of Hanano and Jelly no Puzzle games, revealing that Hanano remains PSPACE-complete under certain restrictions, highlighting the role of block-carrying mechanics in complexity.

Contribution

It demonstrates that Hanano's solvability remains PSPACE-complete under restrictions where Jelly no Puzzle is NP-complete, emphasizing the importance of block-carrying mechanics in computational hardness.

Findings

Hanano remains PSPACE-complete under certain restrictions.

Jelly no Puzzle is NP-complete under similar restrictions.

Block-carrying mechanics are central to the complexity differences.

Abstract

The Hanano Puzzle is a one-player game with irreversible gravity, where the goal is to make colored blocks make contact with flowers of the corresponding color. The game Jelly no Puzzle shares similar mechanics. In general, determining if a given level of each of the two games is solvable is PSPACE-complete. There are also known restrictions under which determining if a level of Jelly no Puzzle is solvable is NP-complete. We find that under the same restrictions, determining if a level of Hanano Puzzle is solvable remains PSPACE-complete. We thus study several restrictions on Hanano, contrast them with known results about Jelly no Puzzle, and posit that the mechanism at the heart of the PSPACE-hardness is the ability for blocks to carry each other.