1. The hardness of the Lemmings game, or Oh no, more NP-completeness proofs;Cormode,2004
2. PushPush and Push-1 are NP-hard in 2D;Demaine,2000
3. PushPush-k is PSPACE-complete;Demaine,2004
4. Computational complexity of two-dimensional platform games;Forišek,2010
5. Gaming is a hard job, but someone has to do it!;Viglietta;Theory Comput. Syst.,2014