# keyDown

[Built-ins](README.md)

Canonical ID: `input.keyDown`. Nederlands: `toetsIngedrukt`.

Asks whether a key is held down **right now** and returns a Boolean: `true` or `false`. Repeatedly asking for the current state is called **polling**. It does not wait for a new press or create a handler that listens for future presses. For a block that starts at the moment a key is pressed, use [keyPressed](keyPressed.md).

The host, the app running the program, supplies the key state. The portable game names are `"left"`, `"right"`, `"up"`, `"down"`, and `"space"`. Native graphical hosts also support common control keys and basic Latin letters and digits (ASCII). A key the host does not provide is reported as not down. Key names are text data and stay the same when you translate source syntax.

## Signature

```text
keyDown(key)
```

## Arguments

| Parameter | Type | Requirement |
|---|---|---|
| `key` | Text | Nonempty host key name; data values are not translated. |

## Return value

`Boolean`.

## Example

```pliro
# language: en
when started():
    let x = 320
    for frame in repeatList(50, none):
        if keyDown("left"):
            set x = x - 2
        clearCanvas("white")
        circle(x, 180, 15, "blue")
        wait(0.04)
```

For about two seconds, holding Left moves the circle left in a graphical host.

## Notes and common mistakes

Use the function name for your source language. Its [canonical ID](../concepts/canonical-identity.md) is a shared documentation label; you do not type that ID as a call. Giving your own variable or function the same name can hide the built-in. Supply the documented [arguments](../concepts/parameters-and-arguments.md) and value types. Pliro reports mismatches when checking can detect them, or when the call runs.

The selected host mediates input. Program replies are bounded to 64 KiB of valid [UTF-8](../concepts/utf-8.md); unavailable input produces E4010. Keyboard names and option strings are data and are not translated with source syntax. Completed prompts are cooperative checkpoints.

## Related entries

[ask](ask.md) · [askNumber](askNumber.md) · [askYesNo](askYesNo.md) · [choose](choose.md) · [Programming guides](../guides/input.md) · [Host support](../guides/hosts.md) · [Calls and arguments](../syntax/calls.md)