AbstractPokemon

abstract class Pokemon extends GameObject{
  int currentHP;
  int maxHP;
  PImage leftImg, rightImg;
  float yVel;
  float GRAV = .5;
  float xVel;
  float xAcc;

  void moveRight() {
    direction = "right";
    xVel = xVel + 9;
    if (xVel <= 20) {  
      xAcc += 0.1;
    } else {
      xAcc = 0;
      xVel = 20;
    }
    xVel = xVel + xAcc;
  }

  void moveLeft() {
    direction = "left";
    xVel = xVel - 9;
    if (xVel >= -20) {
      xAcc -= 0.1;
    } else {
      xAcc = 0;
      xVel = -20;
    }
    xVel = xVel + xAcc;
  }

  void wrap() {
    if (x > width - 50) {
      x = -200;
    } else if (x<-200) {
      x = width - 50;
    }
  }


  void jump() {
    y -= 1;
    if (y >= height - hei - 5) {
      yVel = -10;
    }
  }
  void updatePosition() {
    if (y < height - hei) {
      y = y + yVel;
      yVel = yVel + GRAV;
    } else {
      yVel = 0;
      y = height - hei;
    }

    x = x + xVel;

    if (xVel > 0) {
      xVel = xVel - 1;
    } else if (xVel < 0) {
      xVel = xVel + 1;
    } else {
      xVel = 0;
    }
  }

  boolean isUnconscious() {
    return currentHP <= 0;
  }
}

ElectricPokemon

class Pikachu extends Pokemon {
  
  
  Pikachu(Game g) {
    println("Pikachu initialized!");
    wid = 250;
    hei = 250;
    imgSrc = loadImage("http://cdn.bulbagarden.net/upload/thumb/0/0d/025Pikachu.png/250px-025Pikachu.png");
  }
  
  void attack() {
    println("ZAP!");
    Bolt b = new Bolt(x, y, direction); 
    g.addProjectile(b);
  }

}

FirePokemon

class Charmander extends Pokemon {
  
  
  Charmander(Game g) {
    println("Charmander initialized!");
    wid = 250;
    hei = 250;
    imgSrc = loadImage("http://cdn.bulbagarden.net/upload/thumb/7/73/004Charmander.png/250px-004Charmander.png");
  }
  
  void attack() {
    println("fffffffire!");
    Fireball f = new Fireball(); 
    g.addProjectile(f);
  }
  
}

GameController

class Game {
  ArrayList<Projectile> projectiles;
  Pikachu pik;
  Charmander cha;
  //ArrayList<Platform> platforms;
  
  
  Game(){
    pik = new Pikachu(this);
    cha = new Charmander(this);
    projectiles = new ArrayList<Projectile>();
  }
  
  void tick() {
    updateAllProjectiles();
    drawAllProjectiles();
    updateAllPokemon();
    drawAllPokemon();
  }
  void addProjectile(Projectile p) {
      projectiles.add(p);
  }  
  void updateAllProjectiles() {
    for(int i = 0; i < projectiles.size(); i++){
      Projectile p = projectiles.get(i);
      p.update();
      if(cha.hitTest(p) == true){
        //p.currentHP--;
        cha.jump();
        projectiles.remove(i);
        println("you have been hit!");
      }
    }
  }
  void drawAllProjectiles() {
    for(int i = 0; i < projectiles.size(); i++){
      Projectile p = projectiles.get(i);
      p.drawSelf();
    }
  }
  
  void updateAllPokemon() {
    if (cha != null && pik != null) {
      moveLR();
      jump();
      cha.wrap();
      pik.wrap();
      cha.updatePosition();
      pik.updatePosition();
    }
  }

  void drawAllPokemon() {
    if (cha != null && pik != null) {
      pik.drawSelf();
      cha.drawSelf();
    }  
  }
  
  Pikachu getPikachu() {
    return pik;
  }
  Charmander getCharmander() {
    return cha;
  }
}

GameObject

abstract class GameObject {
  float x, y;
  int wid, hei;
  PImage imgSrc;
  String direction = "none";
  
  int getWid(){
    return wid;
  }
  int getHei(){
    return hei;
  }
  float getX(){
    return x;
  }
  float getY(){
    return y;
  }
  
  boolean hitTest(GameObject otherObj){

    //check X collision
    if(this.getX()+float(this.getWid()) >= otherObj.getX() 
      && this.getX() <= otherObj.getX() + float(otherObj.getWid())){
      //check Y collision
      if(this.getY()+float(this.getHei())  >= otherObj.getY() 
        && this.getY() <= otherObj.getY() + float(otherObj.getHei())){
        return true;
      }
    }
    return false;
  }
  void drawSelf() {
        pushMatrix();
        if (direction =="left") {
            scale(1.0, 1.0);
            image(imgSrc, x, y);
        } else  if(direction == "right"){
            scale(-1.0, 1.0);
            image(imgSrc, -x - imgSrc.width, y);
        } else {
          scale(1.0, 1.0);
          image(imgSrc, x, y);
        }
        popMatrix();
    }
  
}

Gameplay

Game g;

boolean upPressed = false;
boolean downPressed = false;
boolean leftPressed = false;
boolean rightPressed = false;

boolean wPressed = false;
boolean aPressed = false;
boolean sPressed = false;
boolean dPressed = false;

//w,a,s,d,UP,LEFT,DOWN,RIGHT.
boolean keyz[] = new boolean [8];

void setup() {
  g = new Game();
  size(1080, 720);
}

void draw() {
  background(255);
  g.tick();
}

void keyPressed() {
  if (key == 'w') keyz[0] = true;
  if (key == 'a') keyz[1] = true;
  if (key == 's') keyz[2] = true;
  if (key == 'd') keyz[3] = true;
  if (keyCode == UP) keyz[4] = true;
  if (keyCode == LEFT) keyz[5] = true;
  if (keyCode == DOWN) keyz[6] = true;
  if (keyCode == RIGHT) keyz[7] = true;
}

void keyReleased() {
  if (key == 'w') keyz[0] = false;
  if (key == 'a') keyz[1] = false;
  if (key == 's') keyz[2] = false;
  if (key == 'd') keyz[3] = false;
  if (keyCode == UP) keyz[4] = false;
  if (keyCode == LEFT) keyz[5] = false;
  if (keyCode == DOWN) keyz[6] = false;
  if (keyCode == RIGHT) keyz[7] = false;
}

void moveLR() {
  if (keyz[5] == true) {
    g.getPikachu().moveLeft();
  }
  if (keyz[7] == true) {
    g.getPikachu().moveRight();
  }

  if (keyz[6] == true) {
    g.getPikachu().attack();
  }

  if (keyz[1] == true) {
    g.getCharmander().moveLeft();
  }
  if (keyz[3] == true) {
    g.getCharmander().moveRight();
  }

  if (keyz[2] == true) {
    g.getCharmander().attack();
  }
}

void jump() {
  if (keyz[4] == true) {
    g.getPikachu().jump();
  }

  if (keyz[0] == true) {
    g.getCharmander().jump();
  }
}

Projectile

abstract class Projectile extends GameObject {
  float vel;
  float damage;
  
  abstract void update();
}


class Fireball extends Projectile {
  float GRAV;
  color col;
  Fireball() {
    damage = random(5,25);
    GRAV = .5; 
    col = color(255,0,0);
  }
  void update() {
    x = x + vel;
    if (vel > 0) {
      vel = vel / 2;
    }
  }
  void drawSelf() {
    fill(col);
    ellipse(x, y, 20, 20);
  }
}
class Bolt extends Projectile{
  color col;
  Bolt(float startX, float startY, String startDir) {
    x = startX;
    y = startY + 125;
    if (startDir.equals("left")) {
      vel = -25.5;
    } else {
      vel = 25.5;
    }
    damage = random (10,30);
    col = color(#ffff26); 
    println("whoosh");
  }
  void update() {
    x = x + vel;
  }
  void drawSelf() {
    fill(col);
    ellipse(x, y, 20, 20);
  }
}
class Wave extends Projectile{
 color col;
  Wave() {
    damage = random (15,30);
    col = color(#0000ff); 
  }
  void update() {
  }
  void drawSelf() {
    fill(col);
    ellipse(x, y, 20, 20);
  }
}