import java.awt.*;
import javax.swing.*;
//import java.awt.event.*;
//import java.awt.geom.*;

public class PrimalSpire5 extends JApplet {
  
  public void paint(Graphics g) {
    Graphics2D g2d = (Graphics2D) g;
    g2d.setPaint(Color.blue);
    
    int width = getSize().width-1;
    int height = getSize().height-1;
    int midX = width / 2;
    int midY = height / 2;
    int x = midX;
    int y = midY;
 
    int q = 0;
    int count = 1;
    int j = -1;
    
    int dir = 3; //direction
    
    /* you need to add 1 to whatever number you want the spiral to go to and put it where "i <" */
    for (int i = 1; i < 1000001; i++) {
      
      if (dir == 0) { // go east
        x+=1;
      } else if (dir == 1) { // go north
        y-=1;
      } else if (dir == 2) { // go west
        x-=1;
      } else if (dir == 3) { // go south
        y+=1;
      }
      
      if (i < 4) {
        dir++;
      }
      
      if (i == 4) {
        dir = 2;
        q = 5; //just a randomly (read: badly) named variable. I didn't know what to call it.
      }
      
      
      if (i == q) {
        dir++;
        if (i > 9) {
          j++;
        }
        
        if (j % 2 != 0) {
          count++;
        }
        q+= count;
      }
           
      if (dir > 3) {
        dir = 0;
      }
            
      if (is_prime(i)) {
        g2d.setPaint(Color.black);
        g2d.fillRect(x,y,1,1);
      } else {
        g2d.setPaint(Color.blue);
        g2d.fillRect(x,y,1,1);
      } 
    }
  }
  
  
  public static boolean is_prime (int n) {
    boolean prime = true;
    int limit = (int) Math.sqrt (n);  
    
    for (int i = 2; i <= limit; i++) {
      if (n % i == 0) {
        prime = false;
        break;
      }
    }
    
    if (n == 0 || n == 1) {
      return false;
    }
    
    return prime;
  }
  
  
  
  public static void main(String args[]) {
    JFrame frame = new JFrame("Primal Spire");
    JApplet applet = new PrimalSpire5();
    frame.getContentPane().add("Center", applet);
    frame.setSize(300, 250);
    frame.setVisible(true);
  }
}