sneak/Shared/ShmupWorld.cs

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

namespace SemiColinGames {
  public sealed class ShmupWorld : IWorld {
    public class ShmupPlayer {
      public TextureRef Texture = Textures.Yellow2;
      // Center of player sprite.
      public Vector2 Position = new Vector2(48, 1080 / 8);
      public Vector2 HalfSize = new Vector2(16, 10);
      public float Speed = 150f;
    }

    public class Shot {
      static int color = 0;
      public TextureRef Texture;
      public Vector2 Position;
      public Vector2 HalfSize = new Vector2(11, 4);
      public Rectangle Bounds;
      public Vector2 Velocity;
      public Shot(Vector2 position, Vector2 velocity) {
        Texture = (color % 5) switch {
          0 => Textures.Projectile1,
          1 => Textures.Projectile2,
          2 => Textures.Projectile3,
          3 => Textures.Projectile4,
          _ => Textures.Projectile5
        };
        color++;

        Position = position;
        Velocity = velocity;
        Update(0);  // set Bounds
      }

      public void Update(float modelTime) {
        Position = Vector2.Add(Position, Vector2.Multiply(Velocity, modelTime));
        Bounds = new Rectangle(
            (int) (Position.X - HalfSize.X),
            (int) (Position.Y - HalfSize.Y),
            (int) HalfSize.X * 2,
            (int) HalfSize.Y * 2);
      }
    }

    public readonly Rectangle Bounds;
    public readonly ShmupPlayer Player;
    public readonly ProfilingList<Shot> Shots;

    public ShmupWorld() {
      Bounds = new Rectangle(0, 0, 1920 / 4, 1080 / 4);
      Player = new ShmupPlayer();
      Shots = new ProfilingList<Shot>(100, "shots");
    }

    ~ShmupWorld() {
      Dispose();
    }

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

    public void Update(float modelTime, History<Input> input) {
      Vector2 motion = Vector2.Multiply(input[0].Motion, modelTime * Player.Speed);
      Player.Position = Vector2.Add(Player.Position, motion);
      Player.Position.X = Math.Max(Player.Position.X, Player.HalfSize.X);
      Player.Position.X = Math.Min(Player.Position.X, Bounds.Size.X - Player.HalfSize.X);
      Player.Position.Y = Math.Max(Player.Position.Y, Player.HalfSize.Y);
      Player.Position.Y = Math.Min(Player.Position.Y, Bounds.Size.Y - Player.HalfSize.Y);

      foreach (Shot shot in Shots) {
        shot.Update(modelTime);
      }

      if (input[0].Attack && !input[1].Attack) {
        Vector2 shotOffset = new Vector2(12, 2);
        Vector2 shotPosition = Vector2.Add(Player.Position, shotOffset);
        Shots.Add(new Shot(shotPosition, new Vector2(300, 40)));
        Shots.Add(new Shot(shotPosition, new Vector2(300, 20)));
        Shots.Add(new Shot(shotPosition, new Vector2(300, 0)));
        Shots.Add(new Shot(shotPosition, new Vector2(300, -20)));
        Shots.Add(new Shot(shotPosition, new Vector2(300, -40)));
        new Shot(shotPosition, Vector2.Zero);
      }

      Shots.RemoveAll(shot => !Bounds.Intersects(shot.Bounds));
    }
  }
}