Problems with understanding language

Processing Beginners
5

Anyway, all you have to do next is fill in those classes.

This is what I came up with:

// Useful arrays to decode/use direction.
int[] dx = {1, 0, -1, 0};
int[] dy = {0, 1, 0, -1};
int[] dk = { RIGHT, DOWN, LEFT, UP };

class Snake {
  int x, y; // Current head position.
  ArrayList<PVector> tail; // Other segments.
  int d; // Direction of movement;
  boolean isGrowing = false;
  Snake() {
    d = 0;
    tail = new ArrayList();
  }
  void draw() {
    fill(50,200,50);
    stroke(150,200,50);
    rect(x,y,20,20);
    for( int i = 0; i < tail.size(); i++){
      rect(tail.get(i).x,tail.get(i).y,20,20);
    }
  }
  void update() {
    tail.add( new PVector(x,y,d) );
    if( isGrowing ){
      isGrowing = false;
    } else {
      tail.remove(0);
    }
    x += 20*dx[d];
    y += 20*dy[d];
    x += width;
    y += height;
    x %= width;
    y %= height;
  }
  void grow() {
    isGrowing = true;
  }
  void onKeyPressed() {
    for( int i = 0; i < dk.length; i++){
      if( key == CODED && keyCode == dk[i] ){
        d = i;
      }
    }
  }
}

class Food {
  int x, y;
  Food() {
    newPosition();
  }
  void draw() {
    fill(255,0,0);
    stroke(200,0,200);
    ellipse(x+10,y+10,20,20);
  }
  boolean wasEaten(int ox, int oy) {
    if ( x == ox && y == oy ) {
      newPosition();
      return true;
    }
    return false;
  }
  void newPosition() {
    x = 20 * int(random(width/20));
    y = 20 * int(random(height/20));
  }
}

class Timer {
  int time;
  int duration;
  Timer() {
    duration = 100;
    reset();
  }
  void reset() {
    time = millis() + duration;
  }
  boolean alarm() {
    if ( millis() > time ) {
      time = millis() + duration;
      return true;
    }
    return false;
  }
}

// --- Main driving code follows. Notice how simple its logic is to understand!

Snake snake;
Food food;
Timer timer;

void setup() {
  size(600, 400);
  snake = new Snake();
  food = new Food();
  timer = new Timer();
}

void draw() {
  background(0);
  if ( timer.alarm() ) {
    snake.update();
    if ( food.wasEaten( snake.x, snake.y ) ) {
      snake.grow();
    }
  }
  food.draw();
  snake.draw();
}

void keyPressed() {
  snake.onKeyPressed();
}

Using a dynamic structure (an ArrayList) for storing the body segments makes handling the tail a lot easier.

Anyway, this is a MUCH better snake game example to learn from.

2 Likes