Using object's variables

sq_pckmn.pde

Packman p1;
Meal m1;

float distance;

void setup() {
  size(400, 400);
  p1 = new Packman();
  m1 = new Meal();
}

void draw() {
  background(255);
  p1.display();
  p1.control();

  m1.display();

  distance = dist(p1.x, p1.y, m1.x, m1.y);

  if (distance <= p1.size / 2 + m1.size / 2) {
    m1 = new Meal();
    p1.size = p1.size + 10;
  }
}

class Packman {
  float x, y, size, speed;

  Packman() {
    x = random(0, width);
    y = random(0, height);
    size = 20;
    speed = 3;
  }

  void display() {
    rectMode(CENTER);
    fill(#FDFF90);
    rect(x, y, size, size);
  }

  void control() {
    if (keyPressed) {
      if (key == 'd') {
        x = x + speed;
      } else if (key =='a') {
        x = x - speed;
      } else if (key =='s') {
        y = y + speed;
      } else if (key =='w') {
        y = y - speed;
      }
    }

    // Отзеркалниание персонажа
    if (x > width) {
      x = 0;
    } else if (x < 0) {
      x = width;
    }
    if (y > height) {
      y = 0;
    } else if (y < 0) {
      y = height;
    }
  }
}

class Meal {
  float x, y, size;

  Meal() {
    x = random(0, width);
    y = random(0, height);
    size = 20;
  }

  void display() {
    rectMode(CENTER);
    fill(#B3E3A0);
    rect(x, y, size, size);
  }
}