@Override
public void execute(String[] args) {
if (args.length < 1) {
System.out.println("No argument specified. Please specify 'anj', 'dan' or 'debug'");
} else if (args[0].equals("anj")) {
Physics.setPhysicsMode(new PhysicsAnj());
System.out.println("Now using anj's physics.");
} else if (args[0].equals("dan")) {
Physics.setPhysicsMode(new PhysicsDan());
System.out.println("Now using dan's physics.");
} else if (args[0].equals("debug")) {