Step 3: Moving Around

• Declare 2 member variables in Player.cs, and initialize them in the constructor and in OnEnterStage:

public class Player : Entity
{
    float _moveSpeed;
    Axis2 _moveAxis;

    // constructor
    public Player()
    {
        _moveSpeed = 50.0f;
    }

    // called when this entity is added to a stage
    protected override void OnEnterStage(Stage stage)
    {
        base.OnEnterStage(stage);

        _moveAxis = stage.Game.Controls.RightAnalog;
    }

    ...

_moveSpeed should be self-explanatory, and by assigning the RightAnalog property to _moveAxis, we can query it for input from the arrow keys (whereas LeftAnalog would refer to WASD).

• In the player's OnUpdate method, modify the X and Y properties based on which keys are being pressed.

// change position
if(_moveAxis.X.IsPositive)
    X += _moveSpeed * (float)dt;
else if(_moveAxis.X.IsNegative)
    X -= _moveSpeed * (float)dt;

if(_moveAxis.Y.IsPositive)
    Y += _moveSpeed * (float)dt;
else if(_moveAxis.Y.IsNegative)
    Y -= _moveSpeed * (float)dt;

• dt is the delta time (the time since last frame). Factoring it into the movement mode keeps the gameplay framerate independent.

Animating player movement

• Duplicate the player's image and modify it slightly to create a 2-frame walk cycle. Rename them to player_0 and player_1.
• Add another member variable to the Player class for our walk animation:

Animation _walkAnim;

• Create the animation after graphics have been loaded:

protected override void OnLoadGraphics(Graphics graphics)
{
    _walkAnim = graphics.CreateAnimation("Resources", "player_#")(0, 1);
    _walkAnim.Period = 0.25f;
    _walkAnim.IsPaused = true;

    Image image = _walkAnim.GetFrame(0);
    _sprite = Add(new Sprite(_walkAnim, Game.Swatches.Player), new Vector2i(-image.Width / 2, -image.Height / 2));
}

• In the update method, start and stop the animation based on whether the player is moving or not:

// start/stop movement animation
if(_moveAxis.JustBecameZero)
{
    _walkAnim.Reset();
    _walkAnim.IsPaused = true;
}
else if(_moveAxis.JustBecameNonzero)
{
    _walkAnim.IsPaused = false;
}

Facing Moving Direction

• Still in the Player.cs update method, add some code to flip the sprite horizontally when the player is moving to the left:

// flip to face x-axis movement direction
if(_moveAxis.X.IsPositive)
    _sprite.FlipX = false; // image is already facing to the right
else if(_moveAxis.X.IsNegative)
    _sprite.FlipX = true;

Stay in Bounds

• Create a new method in the Player class:

void CheckBounds()
{
    Vector2f gameSize = (Vector2f)Stage.Game.Graphics.Size;
    Vector2f mySize = (Vector2f)_sprite.Size;

    if(X < mySize.X * 0.5f)
        X = mySize.X * 0.5f;
    else if(X > gameSize.X - mySize.X * 0.5f)
        X = gameSize.X - mySize.X * 0.5f;

    if(Y < mySize.Y * 0.5f)
        Y = mySize.Y * 0.5f;
    else if(Y > gameSize.Y - mySize.Y * 0.5f)
        Y = gameSize.Y - mySize.Y * 0.5f;
}

• and call the method at the end of the player's update method.

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