What is happening right now?

import greenfoot.*; public class MyWorld extends World { public MyWorld() { super(800, 600, 1); // Spawn 50 orang normal for (int i = 0; i < 50; i++) { addObject( new People(), Greenfoot.getRandomNumber(getWidth()), Greenfoot.getRandomNumber(getHeight()) ); } // Spawn 1 orang infected secara random People infected = new People(); infected.setInfected(true); addObject(infected,Greenfoot.getRandomNumber(getWidth()),Greenfoot.getRandomNumber(getHeight())); // Spawn ambulance addObject(new Ambulance(), 0, 0); } } ============================================= import greenfoot.*; public class Ambulance extends Actor { private int speed = 5; private int stepDown = 30; private boolean movingRight = true; public void act() { moveZigZag(); healPeople(); } private void moveZigZag() { if (movingRight) { setLocation(getX() + speed, getY()); if (getX() >= getWorld().getWidth() - 1) { movingRight = false; setLocation(getX(), getY() + stepDown); } } else { setLocation(getX() - speed, getY()); if (getX() <= 0) { movingRight = true; setLocation(getX(), getY() + stepDown); } } // Jika sudah mencapai bawah, kembali ke atas if (getY() >= getWorld().getHeight() - 1) { setLocation(getX(), 0); } } private void healPeople() { People p = (People)getOneIntersectingObject(People.class); if (p != null && p.isInfected()) { p.setInfected(false); } } } ===================================================== import greenfoot.*; import java.util.List; public class People extends Actor { private boolean infected = false; private boolean immune = false; private int infectionTimer = 0; public People() { updateImage(); } public void act() { randomMove(); if (infected) { spreadInfection(); infectionTimer++; if (infectionTimer >= 200) { setImmune(true); } } } // Gerak random private void randomMove() { move(4); if (Greenfoot.getRandomNumber(100) < 20) { turn(Greenfoot.getRandomNumber(61) - 30); } if (isAtEdge()) { turn(180); } } // Menularkan ke orang yang disentuh private void spreadInfection() { List<People> people = getIntersectingObjects(People.class); for (People p : people) { if (p != this && !p.isImmune() && !p.isInfected()) { p.setInfected(true); } } } // Mengubah status infected public void setInfected(boolean status) { if (immune) return; infected = status; if (infected) { infectionTimer = 0; } else { infectionTimer = 0; } updateImage(); } public boolean isInfected() { return infected; } // Mengubah menjadi immune public void setImmune(boolean status) { immune = status; if (immune) { infected = false; infectionTimer = 0; } updateImage(); } public boolean isImmune() { return immune; } // Mengganti gambar sesuai status private void updateImage() { if (immune) { setImage("immune.png"); } else if (infected) { setImage("infected.png"); } else { setImage("normal.png"); } } }