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Slide 1 - Adam M. Smith


									                                   Computational Support for Play Testing Game Sketches
                                                        Adam M. Smith    Mark J. Nelson  Michael Mateas

                                                                                                                                                                                                                                  % game mechanics
Research Question                                                      System Architecture                                                                                             Sketch Language                            game_state(position(P)) :- pos(P).
                                                                                                                                                                                                                                  game_event(up_to(P)) :- pos(P).

Problem: Excessive effort makes exploring new designs difficult,                                                                                                                        %-- Answer: 6
                                                                                                                                                                                                                                  possible(up_to(P2)) :-
inhibiting creativity. How do we give game designers access to rich                                                                                                                     happens(mine(a1),0).
                                                                                                                              Designer                                                  happens(drain,1).
backtalk from their designs without requiring too much effort?                                                                                                                          happens(drain,2).
                                                                                                                                                                                                                                      \+ occupied(P2).
Solution: Take a single game definition in our game-sketching                                                                                                                           happens(mine(a2),4).
                                                                                                                                                                                                                                  initiates(up_to(P),position(P)) :-
language and compile this sketch into a human-playable game as                              Analysis Engine                  Game Sketch             Game Engine
                                                                                                                                                                                                                                  terminates(up_to(P2),position(P1)) :-
well as a formal rule system. The playable game can be used for                                                                                                                         happens(mine(canary),7).
                                                                                                                                                                                                                                      pos(P1), pos(P2),
traditional play testing with the designer or her friends, and the                                                                                                                      happens(mine(c0),8).
formal rule system allows machine play testing (solving for play                                                                                                                        happens(down_to(f),10).
                                                                                constraints                                                                            human                                                      initially(position(base)).
traces that meet interesting criteria).                                                              Formal Rule System                  Playable Prototype
                                                                                and queries                                                                           subjects          happens(up_to(a),12).

Game Prototyping                                                                          play traces                                                    play traces
                                                                                                                                                                                        Abstract play trace: When carrying
                                                                                                                                                                                        out “machine play testing” the            % ui bindings
                                                                                       implied properties                                                engagement                     designer can ask our analysis engine to   ui_space(P) :- pos(P).
Game prototypes: working models of an idea that allow the                                   exploits                                                         fun                        find abstract play traces such as the     ui_token(db6k).
                                                                                        puzzle solutions                                                                                trace pictured above that show certain
designer to test its feasibility and make improvements to it.                                                                                                                           properties.    Each line describes a
                                                                                                                                                                                        game event happening at a particular      ui_location(db6k,P) :-
                                                                                                                                                                                        point in the game’s logical timeline.         holds(position(P)).
Physical prototypes: resemble board games; use cards, dice,
                                                                                                                                                                                        Constraints help a designer focus
figurines, hand-drawn maps, etc.; rules are informal and socially                                                              Design                                                   traces on interesting behavior (such as   ui_triggers(ui_click_space(P),up_to(P)).
negotiable; very easy to make changes to physical prototypes                                                                   Insight                                                  “trading in at least six rocks without
                                                                                                                                                                                        ever refueling”).
(even as they are being played)                                                                                                                                                         A common language syntax is used for
                                                                                                                                                                                                                                  Game sketch language sample: Game designers use our
                                                                                                                                                                                                                                  declarative, logic programming language to concisely describe
                                                                      System architecture: Using our system, the designer supplies a single game sketch in exchange for two rich        the original game definition, the
Computational prototypes: primitive versions of real video games;     source of design backtalk. They can get backtalk from their sketch by applying constraints and queries to the     designer-specificed trace constraints
                                                                                                                                                                                                                                  the mechanics and user interface of their game. In this sample
                                                                                                                                                                                                                                  we reproduce a partial sketch illustrating the movement
                                                                      formal rule system or engaging human test subjects with the playable prototype.                                   and queries, and the resulting traces.
use a computer for enforcing rigid rules and performing automatic                                                                                                                                                                 mechanic in DrillBot 6000, both its logical core and its
                                                                                                                                                                                                                                  representation to the player in terms of board-game-like spaces
book-keeping; big leap from informal physical prototypes;                                                                                                                                                                         and tokens.
computational prototypes are resistant to sweeping design changes
Game sketches in our system: target gray area between                  Example Game
traditional categories; use rigid rules on computer with automatic                                                                                                                     Evaluation (getting backtalk from DrillBot 6000)
book-keeping; map to universal, board-game-like, graphical model;
uses declarative, elaboration-tolerant rule representation for                                                                                                                         Designer Effort
                                                                                                                                                                                       • 15 minutes for design and whiteboard play testing
improved flexibility over traditional game implementation tools                                                                                                                        • 1 hour for initial development
                                                                                                                                                                                       • 260 lines of code in sketch language (180 for mechanics, 80 for UI bindings)
Play Testing
                                                                                                                                                                                       Human Play Testing
Self-testing: the designer tries out her own game; good for early                                                                                                                      • Game was fun for designers and three peers (learned that idea was promising)
                                                                                                                                                                                       • One tester felt rushed by timer, easy change to convert to turn-based game to get
stages when rules are still being formalized; quick iteration                                                                                                                          feedback on other properties of the game
                                                                                                                                                                                       • Human players focused on action aspect instead of puzzle/strategy, even in turn-based
Testing with friends: peers do not have access to the “ideal” in                                                                                                                       version (an unexpected reaction)
the designer’s head; give subjective feedback drawn from personal
                                                                                                                                                                                       Machine Play Testing
experience; may not think the same way as target audience              Screenshot of a game sketch: In DrillBot 6000,          Inspiration: Motherload, a popular, commercial Flash    • Original game mechanics allowed undesirable behavior that was masked by particular UI
                                                                       the player moves a mining robot through                 game created by XGen Studios, was the inspiration for
                                                                                                                                                                                       design choices (caught a future bug at design time)
Testing with target audience: most accurate evaluation of a            underground caverns, drilling out rocks of mixed        DrillBot 6000. While our sketch covered only the core
                                                                                                                                                                                       • Search for speed-runs revealed that human players were very cautious with energy
                                                                       value, while managing energy usage and                  mechanics, Motherload includes playfully animated
game; expensive and time consuming; highly sensitive to feel and       periodically returning to the surface to refuel and     graphics, upgradeable items, a large grid-map with a    reserves (but more serious players may find this unnecessary)
polish (not applicable to early stages of development)                 trade items.                                            wide array of rock types, and a comical story.          • Adding a link from top to bottom of the level did not affect the ideal player much (level
                                                                                                                                                                                       design could be preliminarily validated without additional human testing)

EXPRESSIVE INTELLIGENCE STUDIO                                                                                                                                                                                                                        UC SANTA CRUZ

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