Keyboard Input¶

Handle keyboard input using the Input framework property (IInputContext).

Quick Start¶

protected override void OnUpdate(GameTime gameTime)
{
    var deltaTime = (float)gameTime.DeltaTime;

    // WASD movement
    if (Input.IsKeyDown(Key.W)) _position.Y -= _speed * deltaTime;
    if (Input.IsKeyDown(Key.S)) _position.Y += _speed * deltaTime;
    if (Input.IsKeyDown(Key.A)) _position.X -= _speed * deltaTime;
    if (Input.IsKeyDown(Key.D)) _position.X += _speed * deltaTime;

    // One-shot actions
    if (Input.IsKeyPressed(Key.Space)) Jump();
    if (Input.IsKeyPressed(Key.Escape)) PauseGame();
}

Key States¶

IsKeyDown — Held This Frame¶

Returns true every frame the key is held down. Use for continuous actions like movement.

if (Input.IsKeyDown(Key.W))
{
    _position.Y -= speed * deltaTime;
}

IsKeyPressed — Just Pressed This Frame¶

Returns true only on the first frame the key is pressed. Use for one-shot actions.

if (Input.IsKeyPressed(Key.Space))
{
    Jump(); // Once per press, not 60 times per second
}

IsKeyReleased — Just Released This Frame¶

Returns true only on the frame the key is released. Use for charge-release mechanics.

if (Input.IsKeyReleased(Key.E))
{
    ReleaseChargedAttack();
}

Common Patterns¶

WASD + Normalized Diagonal Movement¶

protected override void OnUpdate(GameTime gameTime)
{
    var direction = Vector2.Zero;
    if (Input.IsKeyDown(Key.W)) direction.Y -= 1;
    if (Input.IsKeyDown(Key.S)) direction.Y += 1;
    if (Input.IsKeyDown(Key.A)) direction.X -= 1;
    if (Input.IsKeyDown(Key.D)) direction.X += 1;

    // Normalize prevents diagonal from being 41% faster
    if (direction != Vector2.Zero)
    {
        direction = Vector2.Normalize(direction);
    }

    _position += direction * _speed * (float)gameTime.DeltaTime;
}

Sprint Modifier¶

var speed = Input.IsKeyDown(Key.LeftShift) ? _sprintSpeed : _walkSpeed;
_position += direction * speed * deltaTime;

Key Combinations¶

if (Input.IsKeyDown(Key.LeftControl) && Input.IsKeyPressed(Key.S))
{
    SaveGame();
}

if (Input.IsKeyPressed(Key.Up))    _selectedIndex--;
if (Input.IsKeyPressed(Key.Down))  _selectedIndex++;
if (Input.IsKeyPressed(Key.Return)) SelectMenuItem(_selectedIndex);

The Key Enum¶

Brine2D uses the Key enum (not Keys):

using Brine2D.Input;

Key.A through Key.Z       // Letters
Key.D0 through Key.D9     // Number row
Key.F1 through Key.F12    // Function keys
Key.Space                 // Spacebar
Key.Return                // Enter
Key.Escape                // Escape
Key.LeftShift, Key.RightShift
Key.LeftControl, Key.RightControl
Key.LeftAlt, Key.RightAlt
Key.Up, Key.Down, Key.Left, Key.Right  // Arrow keys
Key.Tab, Key.Backspace, Key.Delete

Text Input¶

For text fields and chat input, use the dedicated text input API:

// Enable text input mode
Input.StartTextInput();

protected override void OnUpdate(GameTime gameTime)
{
    if (Input.IsTextInputActive)
    {
        var text = Input.GetTextInput();
        if (!string.IsNullOrEmpty(text))
        {
            _textBuffer += text;
        }

        if (Input.IsBackspacePressed() && _textBuffer.Length > 0)
        {
            _textBuffer = _textBuffer[..^1];
        }

        if (Input.IsReturnPressed())
        {
            SubmitText(_textBuffer);
            Input.StopTextInput();
        }
    }
}

Troubleshooting¶

Keys not responding¶

Check you're in OnUpdate, not OnRender
Check window has focus — click the game window
Check spelling — it's Key.Space, not Key.Space

Action repeats unexpectedly¶

Use IsKeyPressed, not IsKeyDown:

// ❌ Wrong — repeats every frame
if (Input.IsKeyDown(Key.Space))
{
    Jump(); // Jumps 60 times per second!
}

// ✅ Correct — once per press
if (Input.IsKeyPressed(Key.Space))
{
    Jump();
}

Diagonal movement is faster¶

Normalize the direction vector:

if (direction != Vector2.Zero)
{
    direction = Vector2.Normalize(direction);
}

Summary¶

Method	Usage	Example
`IsKeyDown()`	Key currently held	Movement, sprint
`IsKeyPressed()`	Key just pressed	Jump, shoot, toggle
`IsKeyReleased()`	Key just released	Charge attacks

Next Steps¶

Mouse Input — Handle mouse input
Gamepad Input — Controller support
Input Layers — Priority-based input