/input-systems

name: input-systems
description: >
  Architect game input — action mapping (abstracting keys into named actions),
  rebinding with conflict detection and persistence, multi-device support
  (keyboard, gamepad, touch), analog deadzones, and feel features like input
  buffering and coyote time, plus accessibility. Engine-neutral. Use when the
  user mentions input mapping, rebind controls, gamepad support, deadzone, input
  buffering, coyote time, or accessible controls.

Input systems

Never wire gameplay to raw keys. Map physical inputs (a key, a button, a touch) to named **actions** (`jump`, `interact`, `move`), and let gameplay read actions. That one indirection gives you rebinding, multi-device support, and accessibility almost for free. This skill is the engine-neutral architecture; bind it to `unity-input-system`, `unreal-enhanced-input`, or Godot's `InputMap`.

When to use

• Use to design an input layer: actions, bindings, multiple devices, and a

rebinding UI with conflict detection and saved bindings.

• Use to add analog handling (deadzones, sensitivity) and game-feel features

(input buffering, coyote time).

• Use to make controls accessible (full remapping, hold-vs-toggle, sensitivity,

no required simultaneous presses).

**When *not* to use:** for an engine's concrete input package/API, use `unity-input-system`, `unreal-enhanced-input`, or Godot's InputMap. For the movement/jump *physics* the buffer feeds, see `physics-tuning` and the engine movement skill. Persisting bindings to disk is `save-systems`.

Core workflow

1. **Define actions, not keys.** Gameplay asks "is `jump` pressed?", never "is Space pressed?". Actions are the stable contract; bindings are data. 2. **Bind per device.** Each action holds bindings for keyboard, gamepad, and touch. The active device is whichever last sent input; swap UI prompts to match. 3. **Read the right edge.** Use *pressed-this-frame* (edge) for discrete actions (jump, interact) and *held* (level) for continuous ones (move, aim). Confusing the two causes double-fires or missed presses. 4. **Filter analog input.** Apply a deadzone to sticks/triggers so resting drift reads as zero, and scale sensitivity/curve to taste. 5. **Buffer for feel.** Remember a pressed action for a short window so a slightly early press still fires (input buffering); allow a jump shortly after leaving a ledge (coyote time). 6. **Make rebinding first-class.** A UI that captures the next input, detects conflicts, and persists bindings — and a reset-to-default. Save via `save-systems`. 7. **Verify on every device** and with rebinds: keyboard, gamepad, touch; rebind an action mid-game and confirm gameplay and prompts follow.

Patterns

1. Actions over raw keys; edge vs held

# Gameplay reads ACTIONS. The mapping from key/button to action lives in data.
# Discrete (edge): fire once on the press frame.
if Input.is_action_just_pressed("jump"):
    try_jump()
# Continuous (held): read every frame as an axis.
var move := Input.get_axis("move_left", "move_right")   # -1..1
player.velocity.x = move * RUN_SPEED
# RIGHT: name actions ("jump"); rebinding/devices just change the binding data.
# WRONG: `if Input.is_key_pressed(KEY_SPACE)` — unrebindable, keyboard-only,
# and `is_key_pressed` is a held check that would re-fire jump every frame.

Engine equivalents: Godot `InputMap` + `Input.is_action_just_pressed`; Unity Input System `InputAction` / action maps; Unreal Enhanced Input `Input Actions` + `Input Mapping Contexts`.

2. Analog deadzone and sensitivity

# Raw sticks never rest at exactly zero. Apply a RADIAL deadzone (on the vector
# length), not per-axis, so diagonals aren't clipped into the axes.
func apply_deadzone(stick: Vector2, dead := 0.2, sens := 1.0) -> Vector2:
    var mag := stick.length()
    if mag < dead:
        return Vector2.ZERO                      # inside deadzone -> no movement
    # Rescale so motion ramps from 0 at the edge of the deadzone, not from `dead`.
    var scaled := (mag - dead) / (1.0 - dead)
    return stick.normalized() * pow(scaled, sens)  # sens>1 = finer near center
# WRONG: clamping each axis separately — it carves a square hole and snaps to axes.

3. Input buffering + coyote time (forgiving, responsive feel)

# Buffer: a jump pressed slightly BEFORE landing still triggers on touchdown.
# Coyote: a jump pressed slightly AFTER walking off a ledge still works.
const BUFFER := 0.12   # seconds an early press stays "remembered"
const COYOTE := 0.10   # seconds after leaving ground you can still jump
var _buffer_timer := 0.0
var _coyote_timer := 0.0

func _physics_process(dt):
    _buffer_timer -= dt
    _coyote_timer = COYOTE if is_on_floor() else _coyote_timer - dt
    if Input.is_action_just_pressed("jump"):
        _buffer_timer = BUFFER                  # remember the press
    if _buffer_timer > 0.0 and _coyote_timer > 0.0:
        velocity.y = JUMP_VELOCITY
        _buffer_timer = 0.0; _coyote_timer = 0.0  # consume both so it fires once

4. Rebinding with conflict detection

# Capture the next physical input, reject duplicates, then persist.
func rebind(action: String, event: InputEvent) -> bool:
    for other in actions:                        # conflict check across actions
        if other != action and binding_of(other) == event:
            return false                         # already used -> let UI warn/swap
    set_binding(action, event)                   # engine: erase old + add new event
    save_bindings()                              # persist (see save-systems)
    return true
# Always provide "reset to defaults", and never let the player unbind a key they
# need to reach the menu without an alternative.

Pitfalls

• **Hardcoding keys** in gameplay blocks rebinding, locks out gamepad/touch, and

scatters input logic. Read named actions only.

• **Edge vs held confusion**: using a he