sneak/Shared/SpiderWorld.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System;
using System.Collections.Generic;

namespace SemiColinGames {
  public sealed class SpiderWorld : IWorld {

    public class Spider {
      public TextureRef Texture = Textures.Yellow2;
      public Vector2 Position;
      private Vector2 anchor;
      private float radius;
      private float angle;
      private float momentum = -300;  // radians / second * pixels

      public Spider(float x, float y, float radius, float angle) {
        Position = new Vector2();
        anchor = new Vector2(x, y);
        this.angle = angle;
        this.radius = radius;
      }

      public void Update(float modelTime, History<Input> input) {
        radius += 150 * modelTime * input[0].Motion.Y;
        radius = Math.Clamp(radius, 50, 200);
        float angleChange = modelTime * momentum / radius;
        angle += angleChange;
        float x = anchor.X + radius * (float) Math.Sin(angle);
        float y = anchor.Y + radius * (float) Math.Cos(angle);
        Position.X = x;
        Position.Y = y;
      }

      public void Draw(SpriteBatch spriteBatch) {
        Texture2D texture = Texture.Get;
        Vector2 spriteCenter = new Vector2(texture.Width / 2, texture.Height / 2);
        Vector2 drawPos = Vector2.Floor(Vector2.Subtract(Position, spriteCenter));
        spriteBatch.Draw(texture, drawPos, Color.White);
      }
    }

    public class Anchor {
      public TextureRef Texture = Textures.Terran;
      public Vector2 Position;

      public Anchor(float x, float y) {
        Position = new Vector2(x, y);
      }

      public void Draw(SpriteBatch spriteBatch) {
        Texture2D texture = Texture.Get;
        Vector2 spriteCenter = new Vector2(texture.Width / 2, texture.Height / 2);
        Vector2 drawPos = Vector2.Floor(Vector2.Subtract(Position, spriteCenter));
        spriteBatch.Draw(texture, drawPos, Color.White);
      }
    }

    public readonly Rectangle Bounds;
    public Spider Player;
    public ProfilingList<Anchor> Anchors;

    public SpiderWorld() {
      Bounds = new Rectangle(0, 0, 1280, 720);
      Player = new Spider(200, 720 / 2, 200, 0);

      Anchors = new ProfilingList<Anchor>(100, "anchors");
      Anchors.Add(new Anchor(200, 720 / 2));
      Anchors.Add(new Anchor(600, 720 / 4));
      Anchors.Add(new Anchor(800, 640));
    }

    ~SpiderWorld() {
      Dispose();
    }

    public void Dispose() {
      GC.SuppressFinalize(this);
    }

    public void Update(float modelTime, History<Input> input) {
      Player.Update(modelTime, input);
    }
  }
}