//Draws a half moon, of the specified radius, on the specified location.
//The moon will become visible on the specified frame.

import java.awt.*; // use graphics
  
// EXTRA EFFORT PROBLEM: draw the other half of the moon in the color of
// the background. To do this , you need to pass 'delay' as another parameter 
// to the constructor and keep track of the current color of the background 
// The color of the half-moon may be passed as an argument to the constructor.
//otherwise, its color is yellow
public class Moon extends Sprite {
 int x;  //(x,y) is the point of the moon's center
 int y;
 int radius;
 int appearTime;
 int currentFrame; //number of the current frame in the animation
 NightBackground bg;
 // add more instance variables if needed
 
 //constructors
 public Moon(int x, int y, int radius, int appearTime, NightBackground bg) {
  this.x = x;
  this.y = y;
  this.radius = radius;
  this.appearTime = appearTime;
  currentFrame = 0;
  this.bg = bg;
 }
 
 public void drawState(Graphics g) {
   // if the moon has not appeared yet, do nothing
   // otherwise draw the moon as a vertical half-circle at the position (x,y)
   // add your code here
   if (currentFrame < appearTime) return; //do nothing
   //otherwise, draw the first half of the moon in yellow
   g.setColor(Color.yellow);
   g.fillArc(x-radius, y-radius, 2*radius, 2*radius, 90,180);
   //and the other half of it in the background color,
   //so it will hide any stars behind it.
   g.setColor(bg.color); //this accesses the instance var "color" in the 
   // "ColorBackground" class, which is protected
   g.fillArc(x-radius, y-radius, 2*radius, 2*radius, 270,180);
 }
   
  public void updateState() {
   // add your code here
    currentFrame = currentFrame+1;
 }
 
 public void resetState() {
  // add your code here
   currentFrame = 0;
 }
 
 // For debugging:
   
   public String className() {
    return "Moon";
   }
   
 public String toString() {
  return className() + "["
    + "x=" + x
    + "; y=" + y
    + "; radius=" + radius
    + "; appearTime=" + appearTime
    + "]";
 }
}