Nim

package nim;
import java.util.Scanner;
import java.util.Random;



public class Nim {


    public static void instructions(boolean turn) {
        System.out.println("This game is called Nim...");
        System.out.println("The objective is to force the computer to grab the last stone...");
        System.out.println("You can only take between 1 and 3 stones...");
        System.out.println("You will go first...");
        turn = false;
    }

    public static void game(boolean turn,int stones, int pickedStones) {
        Scanner input = new Scanner(System.in);
        System.out.println("There are "+stones+" stones. ");
        System.out.print("How many stones do you wish to take?(1,2 or 3)");
        pickedStones = input.nextInt();
        if (pickedStones<=3 && pickedStones>=1) {
            stones -= pickedStones;
            turn = false;
         } else if(pickedStones>3){
            System.out.println("C'mon pick a proper number...");
            System.out.print("How many stones do you wish to take?(1,2 or 3)");
            pickedStones = input.nextInt();
            stones -= pickedStones;
            turn = false;

    }}
    public static void isValid(int pickedStones,int stones) {
        if (pickedStones>stones && pickedStones > 3) {
            System.out.print("That is an invalid number");

    }}
    public static void drawStones(int stones,int startStones,int computerPick, boolean turn) {
        Random r = new Random();
        if (stones>=3){
            int computerTurn = r.nextInt(3);
            computerPick = computerTurn;
            turn = true;
        } else if (stones==2){
            int computerTurn = r.nextInt(2);
            computerPick = computerTurn;
            turn = true;
        } else if (stones==1){
            System.out.print("Congrats,you won!");
        } }

    public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    boolean turn;
    turn = false;
    Random rand = new Random();
    Random r = new Random();
    int pickedStones=0;
    int fifteen = 15;
    int thirty = 30;
    int startStones = r.nextInt(thirty-fifteen)+fifteen;
    int stones = startStones;
    int computerPick = 0;
    instructions(turn);
    System.out.println("There are "+stones+" stones. ");
    System.out.print("How many stones do you wish to take?(1,2 or 3)");
    pickedStones = input.nextInt();
    pickedStones -= stones;
    System.out.print(stones+" stones remain...");
    if (pickedStones<=3 && pickedStones>=1) {
        stones -= pickedStones;
        turn = false;

    } else {
            System.out.println("C'mon pick a proper number...");
            System.out.print("How many stones do you wish to take?(1,2 or 3)");
            pickedStones = input.nextInt();
            stones -= pickedStones;
            turn = false;
    while (stones>0) {
        if (turn == true){
            game(turn,stones,pickedStones);
            isValid(stones,pickedStones);
        }
        if (turn == false ){
            drawStones(stones,startStones,computerPick,turn);
        }}}}}