/// <summary>
/// Updates the background screen. Unlike most screens, this should not
/// transition off even if it has been covered by another screen: it is
/// supposed to be covered, after all! This overload forces the
/// coveredByOtherScreen parameter to false in order to stop the base
/// Update method wanting to transition off.
/// </summary>
public override void Update(GameTime gameTime, bool otherScreenHasFocus,
bool coveredByOtherScreen)
{
if (ShowParticles)
{
addTimer += (float)gameTime.ElapsedGameTime.TotalSeconds;
if (addTimer > 0.25f)
{
addTimer -= 0.15f;
particleSystems.Add(new ParticleSystem(
new Vector2(random.Next(ScreenManager.GraphicsDevice.Viewport.Width),
random.Next(ScreenManager.GraphicsDevice.Viewport.Height)),
Vector2.Zero, 64, 256, 128,
1f + 2f * (float)random.NextDouble(), 0.05f, explosionColors));
}
for (int i = 0; i < particleSystems.Count; i++)
{
particleSystems[i].Update((float)gameTime.ElapsedGameTime.TotalSeconds);
if (particleSystems[i].IsActive == false)
{
particleSystems.Garbage.Add(particleSystems[i]);
}
}
particleSystems.Collect();
}
base.Update(gameTime, otherScreenHasFocus, false);
}
/// <summary>
/// Update the world simulation.
/// </summary>
/// <param name="elapsedTime">The amount of elapsed time, in seconds.</param>
public void Update(float elapsedTime)
{
// update all actors
for (int i = 0; i < actors.Count; i++)
{
actors[i].Update(elapsedTime);
}
// update collision
MoveWorld(elapsedTime);
// update particle systems
for (int i = 0; i < particleSystems.Count; i++)
{
particleSystems[i].Update(elapsedTime);
if (particleSystems[i].IsActive == false)
{
particleSystems.Garbage.Add(particleSystems[i]);
}
}
// update the starfield
Vector2 starfieldTarget = Vector2.Zero;
int playingPlayers = 0;
for (int i = 0; i < ships.Length; i++)
{
if (ships[i].Playing)
{
starfieldTarget += ships[i].Position;
playingPlayers++;
}
}
if (playingPlayers > 0)
{
starfield.SetTargetPosition(starfieldTarget / playingPlayers);
}
starfield.Update(elapsedTime);
// check if we can create a new power-up yet
if (powerUpTimer > 0f)
{
powerUpTimer = Math.Max(powerUpTimer - elapsedTime, 0f);
}
if (powerUpTimer <= 0.0f)
{
SpawnPowerUp();
powerUpTimer = powerUpDelay;
}
// clean up the lists
actors.Collect();
particleSystems.Collect();
}
