Games always change

Liad Yosef

Client Architect @ Duda

Pixels and Robots

Village of Boredom

Chapter 1

Pit of Despair

Chapter 1a

Valley of Pixels

Chapter 2

<body>
...
<canvas></canvas>
...
</body>

Game Graphics

<body>
...
<canvas></canvas>
...
</body>

Game Graphics

const canvas = document.querySelector("canvas");
const context = canvas.getContext("2d");

<body>
...
<canvas></canvas>
...
</body>

Game Graphics

const canvas = document.querySelector("canvas");
const context = canvas.getContext("2d");

// later - draw on canvas

context.fillStyle = "#201A23";
context.fillRect(0, 0, 1220, 400);
context.fillStyle = "#8DAA9D";
context.beginPath();
context.rect(square.x, square.y, square.width, square.height);
context.fill();

Game Elements

const player = {
  x: 30,
  y: 90,
  running: false,
  health: 5
}

const enemy = {
  x: 10,
  y: 60,
  velocity: 0.5
}

Game Controls

const keys = {};

window.addEventListener("keydown", onKeyDown);
window.addEventListener("keyup", onKeyUp);

const onKeyDown = (event) => registerKey(event.keyCode, true);
const onKeyUp = (event) => registerKey(event.keyCode, false);

function registerKey(keyCode, isPressed) {
  switch(keyCode) {
    case 37:
      keys.left = isPressed;
    case 38:
      keys.up = isPressed;
    case 39:
      keys.right = isPressed;
    case 40:
      keys.down = isPressed;
  }
}

Game Logic

if(keys.left) {
  batman.velocityX = 0.5;
}
if(keys.down) {
  batman.velocityY = 0.5;
}

batman.x += batman.velcoityX;
batman.y += batman.velocityY;

if(batman.y >= screenHeight) {
  batman.y = screenHeight;
}

if(batman.x === superman.x) {
  batman.lives -= 1;
}
if(player.x === heart.x) {
  batman.lives += 1;
}
if(martha) {
  break;
}

Game Loop

function loop() {
  // magic here
  requestAnimationFrame(loop);
}

requestAnimationFrame(loop);

Game Loop

function loop() {
  // update according to input
  if(keys.left) {
  	batman.velocityX = 0.5;
  }
  batman.x += batman.velcoityX;
  ...
  // run game logic (collisions, etc.)
  if(batman.x === superman.x) {
  	batman.lives -= 1;
  }
  if(player.x === heart.x) {
    batman.lives += 1;
  }
  ...
  // draw on canvas
  context.fillStyle = "#8DAA9D";
  context.rect(square.x, square.y, square.width, square.height);
  context.fill();
  ...
  requestAnimationFrame(loop);
}

requestAnimationFrame(loop);

Sprites

Pixel Art

Game Engines to The Rescue!

Meadow of Efficiency

Chapter 3

bitmelo.com

npx create-react-app 2d-game

// initialize engine
import projectData from "./projectData.json";
const engine = new window.bitmelo.Engine();
engine.addProjectData(projectData);

// game logic

export function init() {
  engine.start();
}

<head>
  <script src="%PUBLIC_URL%/bitmelo.js"></script>
...

index.html

game.js

import * as game from './game/game.js';

function GameWrapper() {
  useEffect(() => {
    game.init();
  }, [])
  return <div className='main'>
    <div id='bitmelo-container'></div>
    ...
  </div>
}

GameWrapper.jsx

engine.onUpdate = () => {
  scr.drawMap(0, 0, -1, -1, 0, 0, 0);
  drawTargets();
  updatePlayer();
  scr.drawText("React Summit 2020!", 50, 90);
};

function drawTargets() {
  targets.forEach((target) => {
    if (!target.wasGrabbed) {
      scr.drawTile(
        61,
        target.x - 8,
        target.y - 8,
        0
      );
    }
  });
}

function updatePlayer() {
  let newX = player.x;
  let isWalking = false;
  if (inp.left.pressed) {
    newX -= player.speed;
    isWalking = true;
    player.flip = 1;
  }
  ...
  const distance = Math.sqrt(dX*dX + dY*dY);
  // player has grabbed a target
  if (distance <= 12) {
    target.wasGrabbed = true;
  }
  ...
  // draw the player
  let frameGID = 1;
  if (player.isWalking) {
    if (player.framesSinceWalkStart % 16 < 8) {
      frameGID = frameGID + 1;
    } else {
      frameGID = frameGID + 2;
    }
  }
}

Mountain of Wisdom

Chapter 4

AI playing Games

Coding the rules

Inferring rules from data

if(player.x > enemy.x) {
  if (player.health > 5) {
    movePlayerRight();
  } else {
    movePlayerLeft();
  }
}
if (player.y > enemy.y) {
  if (player.health > 5) {
    movePlayerUp();
  } else {
    movePlayerDown();
  }
}

const inputs = [
  [input1, result1],
  [input2, result2],
  [input3, result3],
  ...
];
model.train(inputs);
const newResult = model.predict(newInput);

In games, we don't have all the inputs

Reinforcement Learning!

Agent

Environment

Action

State

x: 30

y: 60

enemies: 2

lives: 3

coins: 4

Reinforcement Learning!

Agent

State

Environment

x: 30

y: 60

enemies: 2

lives: 3

coins: 4

Reward

Reinforcement Learning!

Agent

State

Environment

x: 30

y: 60

enemies: 2

lives: 3

coins: 4

Reinforcement Learning!

Agent

New State

Environment

x: 30

y: 60

enemies: 2

lives: 3

coins: 5

How good is this action?

+

Immediate Reward

Expected rewards from new state

Value Table

	UP	DOWN	LEFT	RIGHT
State 1 (x: 20, y: 30)	12	5	15	4
State 2 (x: 10, y: 10)	11	8	9	3
State 3 (x: 10, y: 20)	8	7	9	10
...	...	...	...	...

Reward: 2

Value Table

	UP	DOWN	LEFT	RIGHT
State 1 (x: 20, y: 30)	12	5	15	4
State 2 (x: 10, y: 10)	11	8	9	3
State 3 (x: 10, y: 20)	8	7	9	10
...	...	...	...	...

Value Table

	UP	DOWN	LEFT	RIGHT
State 1 (x: 20, y: 30)	12	5	15	4
State 2 (x: 10, y: 10)	12	8	9	3
State 3 (x: 10, y: 20)	8	7	9	10
...	...	...	...	...

Value Table

	FLAP	NOTHING
Distance1, Height1	12	5
Distance2, Height2	12	8
Distance3, Height3	8	7
...	...	...

Value Network

Feeding Frames

Exploration

Cool, but.

https://github.com/aaronhma/awesome-tensorflow-js

https://www.metacar-project.com/

Cool, but.

https://openai.com/blog/gym-retro/

// create an environment object
var env = {};
env.getNumStates = function() { return 8; }
env.getMaxNumActions = function() { return 4; }

// create the DQN agent
var spec = { alpha: 0.01 } // see full options on DQN page
agent = new RL.DQNAgent(env, spec); 

setInterval(function(){ // start the learning loop
  var action = agent.act(s); // s is an array of length 8
  //... execute action in environment and get the reward
  agent.learn(reward); // the agent improves its Q,policy,model, etc. reward is a float
}, 0);

https://github.com/karpathy/reinforcejs

export function fireAction(key, wait = 0) {
  fireWindowEvent(key, true);
  setTimeout(async () => {
    fireWindowEvent(key, false);
  }, wait);
}

export function getActor() {
  return [player.x, player.y];
}

export function getTarget() {
  return [target.x, target.y];
}

game.js

env.getNumStates = () => 4;
env.getMaxNumActions = () => 4;
agent = new RL.DQNAgent(env, spec);

[actor, target] = [getActor(), getTarget()];

const distance_before = getDistance(actor, target);

const action = agent.act([actor.x, actor.y, target.x, target.y]);
const actions = {
  0: () => fireAction("ArrowRight"),
  1: () => fireAction("ArrowLeft"),
  2: () => fireAction("ArrowUp"),
  3: () => fireAction("ArrowDown")
}
actions[action]();

[actor, target] = [getActor(), getTarget()];

const distance_after = getDistance(actor, target);

let reward =
    actorInEdge
	? -(distance_after / 300)
	: (distance_before - distance_after) / (distance_before);

agent.learn(reward);

ai.js

const saved = agent.toJSON();
...
agent.fromJSON(saved);

We have AI!

River of Opportunities

Chapter 5

Let's explore!

let inputs = [actor.x, actor.y, target.x, target.y, target.direction]

ai.js

let reward = (distance_before - distance_after) / (distance_before);

ai.js

let reward = - (distance_before - distance_after) / (distance_before);

let reward = (-1 * gettingCloserToMorty) + gettingCloserToTarget

ai.js

Village of Boredom

Chapter 1

Valley of Pixels

Chapter 2 River of Opportunities

Chapter 5

Chapter 3

Meadow of Efficiency

Pit of Despair

Chapter 1a

Chapter 4 Mountain of Wisdom

Just do it.

You're awesome!

QUESTIONS?

@liadyosef

https://github.com/liady/rl-games

https://rl-games-ai.netlify.app/

Games & AI

By Liad Yosef

Games & AI

Build games for your AI to play.

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