human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "pushpush and push 1 are np hard in 2d"
  Abstract: We prove that two pushing-blocks puzzles are intractable in 2D. One of our constructions improves an earlier result that established intractability in 3D [OS99] for a puzzle inspired by the game PushPush. The second construction answers a question we raised in [DDO00] for a variant we call Push-1. Both puzzles consist of unit square blocks on an integer lattice; all blocks are movable. An agent may push blocks (but never pull them) in attempting to move between given start and goal positions. In the PushPush version, the agent can only push one block at a time, and moreover when a block is pushed it slides the maximal extent of its free range. In the Push-1 version, the agent can only push one block one square at a time, the minimal extent---one square. Both NP-hardness proofs are by reduction from SAT, and rely on a common construction.

Connected through hyperedge HE-1 (induced by source paper "the computational complexity of angry birds"):
  with members:
    - "the computational complexity of portal and other 3d video games"
    - "pspace completeness of bloxorz and of games with 2 buttons"
    - "braid is undecidable"
    - "a bayesian ensemble regression framework on the angry birds game"
    - "bejeweled candy crush and other match three games are np hard"
    - "towards a theory of mind inspired generic decision making framework"
    - "candy crush is np hard"
    - "classic nintendo games are computationally hard"

Connected through hyperedge HE-2 (induced by source paper "on rearrangement of items stored in stacks"):
  with members:
    - "fast high quality dual arm rearrangement in synchronous monotone tabletop setups"
    - "efficient high quality stack rearrangement"
    - "complexity results and fast methods for optimal tabletop rearrangement with overhand grasps"
    - "on the hardness of unlabeled multi robot motion planning"

Connected through hyperedge HE-3 (induced by source paper "planning with selective physics based simulation for manipulation among movable objects"):
  with members:
    - "randomized physics based motion planning for grasping in cluttered and uncertain environments"

Connected through hyperedge HE-4 (induced by source paper "particle computation complexity algorithms and logic"):
  with members:
    - "particle computation designing worlds to control robot swarms with only global signals"
    - "universal computation with arbitrary polyomino tiles in non cooperative self assembly"
    - "intrinsic universality in tile self assembly requires cooperation"
    - "limitations of self assembly at temperature 1"
    - "pspace completeness of sliding block puzzles and other problems through the nondeterministic constraint logic model of computation"
    - "playing games with algorithms algorithmic combinatorial game theory"

Connected through hyperedge HE-5 (induced by source paper "push pull block puzzles are hard"):
  with members:
    - "bejeweled candy crush and other match three games are np hard"
    - "classic nintendo games are computationally hard"
    - "motion planning with pull moves"
    - "pspace completeness of sliding block puzzles and other problems through the nondeterministic constraint logic model of computation"

Connected through hyperedge HE-6 (induced by source paper "efficient high quality stack rearrangement"):
  with members:
    - "motion planning for unlabeled discs with optimality guarantees"
    - "on the hardness of unlabeled multi robot motion planning"
    - "multi agent path planning and network flow"

Connected through hyperedge HE-7 (induced by source paper "similar part rearrangement with pebble graphs"):
  with members:
    - "k color multi robot motion planning"
    - "sampling based algorithms for optimal motion planning"

Connected through hyperedge HE-8 (induced by source paper "particle computation designing worlds to control robot swarms with only global signals"):
  with members:
    - "pspace completeness of sliding block puzzles and other problems through the nondeterministic constraint logic model of computation"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.CG(Computational Geometry)