// Called every frame, passing in `dt` since the last frame. `dt`
// is short for `deltaTime` and is measured in seconds.Multiplying
// this by any changes we wish to make in our game will allow our
// game to perform consistently across all hardware; otherwise, any
// changes we make will be applied as fast as possible and will vary
// across system hardware.
public override async Task Update(TimeSpan dt)
{
switch (gameState)
{
case GameState.Serve:
// before switching to play, initialize ball's velocity based
// on player who last scored
ball.Dy = Random.Next(-50, 50);
if (servingPlayer == 1)
{
ball.Dx = Random.Next(140, 200);
}
else
{
ball.Dx = -Random.Next(140, 200);
}
break;
case GameState.Play:
// detect ball collision with paddles, reversing dx if true and
// slightly increasing it, then altering the dy based on the position
// at which it collided, then playing a sound effect
if (ball.Collides(player1))
{
ball.Dx = -ball.Dx * 1.03;
ball.X = player1.X + 5;
// keep velocity going in the same direction, but randomize it
if (ball.Dy < 0)
{
ball.Dy = -Random.Next(10, 150);
}
else
{
ball.Dy = Random.Next(10, 150);
}
await Sounds["paddle_hit"].Play();
}
if (ball.Collides(player2))
{
ball.Dx = -ball.Dx * 1.03;
ball.X = player2.X - 4;
// keep velocity going in the same direction, but randomize it
if (ball.Dy < 0)
{
ball.Dy = -Random.Next(10, 150);
}
else
{
ball.Dy = Random.Next(10, 150);
}
await Sounds["paddle_hit"].Play();
}
// detect upper and lower screen boundary collision, playing a sound
// effect and reversing dy if true
if (ball.Y <= 0)
{
ball.Y = 0;
ball.Dy = -ball.Dy;
await Sounds["wall_hit"].Play();
}
// -4 to account for the ball's size
if (ball.Y >= VirtualHeight - 4)
{
ball.Y = VirtualHeight - 4;
ball.Dy = -ball.Dy;
await Sounds["wall_hit"].Play();
}
// if we reach the left edge of the screen, go back to serve
// and update the score and serving player
if (ball.X < 0)
{
servingPlayer = 1;
player2Score++;
await Sounds["score"].Play();
// if we've reached a score of 10, the game is over; set the
// state to done so we can show the victory message
if (player2Score == 10)
{
winningPlayer = 2;
gameState = GameState.Done;
}
else
{
gameState = GameState.Serve;
// places the ball in the middle of the screen, no velocity
ball.Reset();
}
}
// if we reach the right edge of the screen, go back to serve
// and update the score and serving player
if (ball.X > VirtualWidth)
{
servingPlayer = 2;
player1Score++;
await Sounds["score"].Play();
// if we've reached a score of 10, the game is over; set the
// state to done so we can show the victory message
if (player1Score == 10)
{
winningPlayer = 1;
gameState = GameState.Done;
}
else
{
gameState = GameState.Serve;
// places the ball in the middle of the screen, no velocity
ball.Reset();
}
}
break;
}
//
// paddles can move no matter what state we're in
//
// player 1
if (Keyboard.IsDown(Key.W))
{
player1.Dy = -PaddleSpeed;
}
else if (Keyboard.IsDown(Key.S))
{
player1.Dy = PaddleSpeed;
}
else
{
player1.Dy = 0;
}
// player 2
if (Keyboard.IsDown(Key.Up))
{
player2.Dy = -PaddleSpeed;
}
else if (Keyboard.IsDown(Key.Down))
{
player2.Dy = PaddleSpeed;
}
else
{
player2.Dy = 0;
}
// update our ball based on its DX and DY only if we're in play state;
// scale the velocity by dt so movement is framerate - independent
if (gameState == GameState.Play)
{
ball.Update(dt);
}
player1.Update(dt);
player2.Update(dt);
}
