Platformer2D/Platformer2D.Core/Game/Gem.cs

   1 #region File Description
   2 //-----------------------------------------------------------------------------
   3 // Gem.cs
   4 //
   5 // Microsoft XNA Community Game Platform
   6 // Copyright (C) Microsoft Corporation. All rights reserved.
   7 //-----------------------------------------------------------------------------
   8 #endregion
   9
  10 using System;
  11 using Microsoft.Xna.Framework;
  12 using Microsoft.Xna.Framework.Graphics;
  13 using Microsoft.Xna.Framework.Audio;
  14
  15 namespace Platformer2D
  16 {
  17     /// <summary>
  18     /// A valuable item the player can collect.
  19     /// </summary>
  20     class Gem
  21     {
  22         private Texture2D texture;
  23         private Vector2 origin;
  24         private SoundEffect collectedSound;
  25
  26         public readonly int PointValue = 30;
  27         public readonly Color Color = Color.Yellow;
  28
  29         // The gem is animated from a base position along the Y axis.
  30         private Vector2 basePosition;
  31         private float bounce;
  32
  33         public Level Level
  34         {
  35             get { return level; }
  36         }
  37         Level level;
  38
  39         /// <summary>
  40         /// Gets the current position of this gem in world space.
  41         /// </summary>
  42         public Vector2 Position
  43         {
  44             get
  45             {
  46                 return basePosition + new Vector2(0.0f, bounce);
  47             }
  48         }
  49
  50         /// <summary>
  51         /// Gets a circle which bounds this gem in world space.
  52         /// </summary>
  53         public Circle BoundingCircle
  54         {
  55             get
  56             {
  57                 return new Circle(Position, Tile.Width / 3.0f);
  58             }
  59         }
  60
  61         /// <summary>
  62         /// Constructs a new gem.
  63         /// </summary>
  64         public Gem(Level level, Vector2 position)
  65         {
  66             this.level = level;
  67             this.basePosition = position;
  68
  69             LoadContent();
  70         }
  71
  72         /// <summary>
  73         /// Loads the gem texture and collected sound.
  74         /// </summary>
  75         public void LoadContent()
  76         {
  77             texture = Level.Content.Load<Texture2D>("Sprites/Gem");
  78             origin = new Vector2(texture.Width / 2.0f, texture.Height / 2.0f);
  79             collectedSound = Level.Content.Load<SoundEffect>("Sounds/GemCollected");
  80         }
  81
  82         /// <summary>
  83         /// Bounces up and down in the air to entice players to collect them.
  84         /// </summary>
  85         public void Update(GameTime gameTime)
  86         {
  87             // Bounce control constants
  88             const float BounceHeight = 0.18f;
  89             const float BounceRate = 3.0f;
  90             const float BounceSync = -0.75f;
  91
  92             // Bounce along a sine curve over time.
  93             // Include the X coordinate so that neighboring gems bounce in a nice wave pattern.
  94             double t = gameTime.TotalGameTime.TotalSeconds * BounceRate + Position.X * BounceSync;
  95             bounce = (float)Math.Sin(t) * BounceHeight * texture.Height;
  96         }
  97
  98         /// <summary>
  99         /// Called when this gem has been collected by a player and removed from the level.
 100         /// </summary>
 101         /// <param name="collectedBy">
 102         /// The player who collected this gem. Although currently not used, this parameter would be
 103         /// useful for creating special power-up gems. For example, a gem could make the player invincible.
 104         /// </param>
 105         public void OnCollected(Player collectedBy)
 106         {
 107             collectedSound.Play();
 108         }
 109
 110         /// <summary>
 111         /// Draws a gem in the appropriate color.
 112         /// </summary>
 113         public void Draw(GameTime gameTime, SpriteBatch spriteBatch)
 114         {
 115             spriteBatch.Draw(texture, Position, null, Color, 0.0f, origin, 1.0f, SpriteEffects.None, 0.0f);
 116         }
 117     }
 118 }