UMD Game Design Club 2D Game Workshop 1

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UMD Game Design Club2D Game Workshop 1

• website
• http//www.cis.umassd.edu/u_ddaniels/gdc

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Goals

• To give an introduction to the 2D platform game
  we'll be using for the competition.
• To get hands on experience developing add-ons to
  the 2D platform game.
• Create a new bad guy for the game.
• Add more complex movements, (jumping around, and
  over obstacles)
• Add more complex behavior (tracking the player)

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Game Competition

• The first GDC game competition involves modifying
  an existing 2D platform game to create your own
  unique game.
• You can edit the
• images and tiles used in the game
• edit how the game plays, modify the physics etc.

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Creating a 2D Platform game

• Platform games are games in which player runs and
  jumps from platform to platform, avoiding bad
  guys and collecting power ups.
• To create a platform game you must learn about
• tile-based maps
• map files
• collision detection
• power-ups
• bad guys
• parallax background scrolling

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Graphics Package

• Contains the basic classes for running graphics
• Sets up the output device for desired output
• Contains Animation, NullRepaintManager,
  ScreenManager, and Sprite
• Animation stores a list of images and times to
  display them
• ScreenManager sets up a full screen display
• Sprite is an animation with a location and speed
• NullRepaintManager is RepaintManager that does
  nothing

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Input Package

• Handles the input from the keyboard or mouse
• Can map actions to different keys
• Contains GameAction, InputManager
• GameAction toggles state when key is pressed or
  released
• Can set action type, continuous action, or single
  action
• InputManager sets specified keys to GameActions

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Tile-Game package

• Loads in the maps and sprite images for different
  objects
• Runs the game through GameManager
• TileMap holds the map of the level
• TileMapRenderer draws the map onto the screen

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Sprites Package

• Handles the different sprites in the game
• Contains Creature, Player, PowerUp, and enemy
  classes
• Creature is base class for enemy and player
• Enemy has a specified movement pattern
• Player handles player movement and state
• PowerUp is an object that can be picked up by the
  player

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Creating a Tile-Based Map

• A tile-based map is composed of several image
  tiles on a grid.
• Like creating a game with building blocks
• Makes it easy to determine what's solid and
  what's empty on the map.
• See TileMap.java class for details

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Loading Tile Maps

• Tile maps can be stored in text files, which can
  contain characters that represent specific tiles.
• This allows for easy creation and storage of
  levels for your game.
• See TileMap.loadMap() for details.

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Example Tile Map
Map file for tile-based game (Lines that
start with '' are comments) The tiles are
(Space) Empty tile A..Z Tiles A through
Z o Star ! Music Note
Goal 1 Bad Guy 1 (grub) 2
Bad Guy 2 (fly) 3 Bad Guy 3 (monkey)


o o
o o o
o o o 3 o o o
o o IIIIIII III
o o 2
3 o 2
2 EF 2EF 3
3 EF EGD 3 3
EGD EF 1 CD 31 EGAD
EGAD BBBBBBBBGHBBBBBBBGHBBBBBBBBBBBBBB
BBBBBBBBBBBBBBBBBBGAAHBBBBBBBBBBB
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Badguys

• Bad guys are the creatures in the game that stop
  the player from reaching their goal.
• In this workshop we'll be creating a new bad guy.
• We'll take the existing framework used to create
  the other bad guys, and extend it, to make a more
  complex bad guy.
• The new bad guy will be able to leap around and
  will also be able to follow and track the player.

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BAD MONKEY!

• The Bad Guy we'll be creating is the evil
  MONKEY!!
• He is a ruthless, chaotic monkey who leaps around
  the level, viciously hunting down the player.

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Creating the new creature

• To create the new Creature we create Monkey.java
  in com.brackeen.javagamebook.tilegame.sprites.
• The Monkey class extends the Creature class. The
  Creature class contains a lot of useful
  functionality that we'll be leveraging.
• There is a basic Monkey.java class in your
  workspace, let's take a look at it now.

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Adding the new Creature to the 2D Game

• Now that we created the object how do we get it
  to display in a tile map that we create.
• We must modify the ResourceManager.java class.
• This class loads and manages tile Images and
  "host" Sprites used in the game. Game Sprites are
  cloned from "host" Sprites.
• We can use the other bad guy sprites as a
  template for our sprite.

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Adding Monkey to ResourceManger.java

• The basic steps to add a new bad guy to the
  ResourceManager.java are as follows (follow the
  //TODO sections in the code)
• declare the host sprite as a class variable this
  will be used so we can clone multiple instances
  of the same sprite.
• Map the sprite to a character ('3',
  '4','k'...etc) so that when we read the tile map
  text file in we can place the bad guy on the map.
• Load sprite animation images, and create
  animation.
• Lets do this now and get a basic monkey creature
  running. Use maps/map1.txt as it already has
  functionality to include a monkey creature, just
  use character '3' to represent that enemy.

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Making the creature jump

• To make the creature jump we have to override
  it's update() method.
• The update() method gets called every time a
  frame is drawn, and it updates the creatures
  state.
• Important game state variables passed with the
  update method.
• elapsedTime the time since the last frame was
  drawn
• totalElapsedTime the total time the game has
  been running

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Making the monkey jump every 2 seconds

• How do we make the monkey jump every 2 seconds?
• You must set a jumpInterval, and then use the
  elapsedTime and totalElapsedTime to figure out
  when the monkey should call the jump() method.
• Be careful a straight modulus comparison against
  totalTime will not work, because update() is
  called with timeIntervals, not discrete
  quantities.
• You must check if the elapsedTime passed the time
  you were waiting for.
• For example if you were waiting for 2 seconds
  totalElapsedTime, you have to realize that if the
  elapsedTime goes from 1 to 3, then we passed 2 so
  we should jump().

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
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Monkey Jump Solution

• public void update(long elapsedTime)
• // Call super to maintain animation behavior
• super.update(elapsedTime)
• //See if its time for the monkey to jump
• //Because time comes in at intervals we have to
  make sure that
• //we jump in whichever elapsedTime interval that
  the timer has
• // gone off in.
• if((totalElapsedTime jumpInterval)-elapsedTim
  elt0)
• //Make the monkey jump if he's not already in
  the air
• jump()

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Additional behavior

• Make monkey jump at a slightly different time
  every jump. Use the RandomUtil.getInt() method
  after the monkey jumps.
• Tracking the player.
• Add code in the GameManager.java class.
• add code to the updateCreature() method.
• Make sure creature is tracking the player
  creature.isTracking(), then make sure creature's
  horizontal (X) velocity is moving towards the
  player's position.

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More Ideas to Expand The Game

• Better collision detection, and handling.
• Interactive tiles, breakable tiles, open doors,
  adds a puzzle element to the game.
• walk-thru tiles that could allow users to pass
  into a tunnel or a cave.
• Use different images for different actions, such
  as jumping, dying, collecting power up.
• Better map-to-map transitions create a loading
  screen
• Keep track of powerup collection add a scoring
  element to the game.
• More bad guys, more levels, different images!

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Next week

• We'll be presenting another workshop on 2D Game
  Design, to give people more experience developing
  the 2D platform game.