A good snowman is hard to plan

Miquel Bofill, Cristina Borralleras, Joan Espasa Arxer, Gerard Martín, Gustavo Patow

Research output: Contribution to conferencePaperpeer-review


In this work we face a challenging puzzle video game: A Good Snowman is Hard to Build. The objective of the game is to build snowmen by moving and stacking snowballs on a discrete grid. For the sake of player engagement with the game, it is interesting to avoid that a player finds a much eas- ier solution than the one the designer expected. Therefore, having tools that are able to certify the optimality of solutions is crucial. Although the game can be stated as a planning problem and can be naturally modelled in PDDL, we show that a direct translation to SAT clearly outperforms off-the-shelf state-of- the-art planners. As we show, this is mainly due to the fact that reachability properties can be easily modelled in SAT, allowing for shorter plans, whereas using axioms to express a reachability derived predicate in PDDL does not result in any significant reduction of solving time with the considered planners. We deal with a set of 51 levels, both original and crafted, solving 43 and with 8 challenging instances still remaining to be solved.
Original languageEnglish
Number of pages9
Publication statusPublished - 9 Jul 2023
EventKnowledge Engineering for Planning and Scheduling - Prague
Duration: 9 Jul 2023 → …


WorkshopKnowledge Engineering for Planning and Scheduling
Abbreviated titleKEPS
Period9/07/23 → …
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