/// <summary>
/// Initializes a new <see cref="UfoController"/>.
/// </summary>
public UfoController()
{
JsonObject jsonObject = MainGame.Context.Content.Load <JsonObject>("UfoScores");
scores = JsonConvert.DeserializeObject <int[]>(jsonObject.JsonSource);
spaceInvadersFont = MainGame.Context.Content.Load <SpriteFont>("SpaceInvadersFont");
timeToSpawn = Random.Range(MinimumSpawnTime, MaximumSpawnTime);
ufoTexture = MainGame.Context.MainTextureAtlas["ufo"];
BoundingRectangle = new RectangleF(0, 0, ufoTexture.Width * MainGame.ResolutionScale,
ufoTexture.Height * MainGame.ResolutionScale);
flashScore = false;
}
/// <summary>
/// Update the <see cref="UfoController"/>.
/// </summary>
/// <param name="deltaTime"></param>
public void Update(float deltaTime)
{
if (MainGame.Context.GetGameScreen <GameplayScreen>(GameScreenType.Gameplay).IsFrozen)
{
return;
}
float ufoWidth = ufoTexture.Width * MainGame.ResolutionScale;
if (flashScore)
{
UpdateScoreFlash(deltaTime);
return;
}
if (isUfoActive)
{
BoundingRectangle.X += HorizontalSpeed * movementDirection * deltaTime;
// Check if the UFO has gone out of bounds
if (movementDirection == 1 && BoundingRectangle.X - ufoWidth * MainGame.ResolutionScale > MainGame.GameScreenWidth ||
movementDirection == -1 && BoundingRectangle.X < -ufoWidth)
{
Destroy(false);
}
}
else
{
timeToSpawn -= deltaTime;
if (!(timeToSpawn <= 0))
{
return;
}
// A 50% chance to spawn on the left side.
bool left = Random.Value() > 0.5f;
movementDirection = left ? 1 : -1;
isUfoActive = true;
float positionY = GameplayScreen.TopVerticalBoundary + ufoTexture.Height * MainGame.ResolutionScale + VerticalSpawnPadding;
float positionX = left ? -ufoWidth : MainGame.GameScreenWidth + ufoWidth;
BoundingRectangle.Position = new Vector2(positionX, positionY);
timeToSpawn = Random.Range(MinimumSpawnTime, MaximumSpawnTime);
}
}
/// <summary>
/// <para>
/// Gets the time until an <see cref="Enemy"/> can attack, in seconds, implemented as a range
/// between a pair of exponential functions.
/// </para>
/// <remarks>
/// More formally, the upper and lower bounds of the enemy attack times are given by a pair of functions
/// f(x) and g(x) where f(x) represents the maximum time, g(x) represents the minimum time, and x represents the
/// change in the vertical distance, in pixels (x in [0, d] where d represents the max vertical distance).
/// The enemy attack time, t(x), is defined as a random value uniformly distributed on [f(x), g(x)]: t(x) ~ U([f(x), g(x)])
/// where U represents the distribution function. For the full equations, see <see href="https://www.desmos.com/calculator/wzpbqmwmwt"></see>.
/// </remarks>
/// </summary>
/// <returns></returns>
private float GetEnemyAttackTime()
{
// The initial maximum time until an enemy attacks, in seconds; the value of g(0).
const float initialMaximumTime = 30;
// The initial minimum time until an enemy attacks, in seconds; the value of f(0).
const float initialMinimumTime = 2;
// The final maximum time until an enemy attacks, in seconds; the value of g(d).
const float finalMaximumTime = 6;
// The final minimum time until an enemy attacks, in seconds; the value of f(d).
const float finalMinimumTime = 1;
float validVerticalDistance = 1 / (MainGame.Context.GetGameScreen <GameplayScreen>(GameScreenType.Gameplay).BarrierGroup[0].Rectangle.Top - StartingPosition.Y);
float b1 = (float)Math.Pow(initialMinimumTime / initialMaximumTime, validVerticalDistance);
float b2 = (float)Math.Pow(finalMinimumTime / finalMaximumTime, validVerticalDistance);
float distance = boundingRectangle.Y - StartingPosition.Y;
float maximumTime = initialMaximumTime * (float)Math.Pow(b1, distance);
float minimumTime = finalMaximumTime * (float)Math.Pow(b2, distance);
return(Random.Range(minimumTime, maximumTime));
}
/// <summary> /// Retrieves a random projectile prototype with the specified type. /// </summary> /// <param name="type">The type of the projectile prototype.</param> private Projectile GetRandomProjectilePrototype(ProjectileType type) => projectilePrototypes[type][Random.Range(projectilePrototypes[type].Count)];
