> For the complete documentation index, see [llms.txt](https://0x29a.gitbook.io/0x29a-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://0x29a.gitbook.io/0x29a-docs/introduction/lifecycle.md).

# Lifecycle & scheduler

The engine drives a `__neuro_tick(dt)` once per frame, on the render thread. The bootstrap uses that to implement a simple scheduler exposed as `_29a.*` (with `neuro` as a back-compat alias — `neuro.on_frame` behaves identically to `_29a.on_frame`).

## `_29a.time()`

Returns the accumulated time, in milliseconds, since the engine started.

## `_29a.on_frame(fn)`

```lua
local id = _29a.on_frame(function()
    -- runs once per rendered frame
end)
```

* **Returns:** an `id` (integer) that can be passed to `_29a.remove(id)`.
* Errors inside `fn` are caught with `pcall` and printed to the console — an exception doesn't take down the other callbacks or the overlay.

## `_29a.after(ms, fn)`

Schedules `fn` to run **once**, after `ms` milliseconds.

```lua
_29a.after(3000, function()
    print("3 seconds have passed")
end)
```

## `_29a.every(ms, fn)`

Like `after`, but repeats indefinitely every `ms` milliseconds.

```lua
local id = _29a.every(1000, function()
    print("1s tick")
end)

-- later:
_29a.remove(id)
```

* **Returns:** an `id` for use with `_29a.remove`.

## `_29a.remove(id)`

Removes an `on_frame` callback or a timer (`after`/`every`) by the `id` returned when it was registered.

## `_29a.clear()`

Removes **every** frame callback and every timer at once. Useful from a thread's `__neuro_on_stop`, or when manually reloading a script.

## `_29a.register_settings(...)` / `_29a.menu_is_open()`

Thin bridges to the script-settings registry in the overlay's settings tab, and to whether the main menu (INSERT) is currently open — useful to pause heavy logic (scans, drawing) when the user isn't looking at the menu.

```lua
if _29a.menu_is_open() then
    -- only draw debug overlays while the menu is visible
end
```

## Execution order

1. The DLL injects and creates the main Lua state (`Engine::MakeState`).
2. The bootstrap (compiled, not a file) runs first — it defines `_29a`, `bind`/`unbind`, the global helpers.
3. Your scripts (`scripts/` folder) load on top of that.
4. Every frame, `__neuro_tick(dt)` fires the `on_frame` callbacks, processes pending timers, then the hotkeys registered via `bind`.

See also [Hotkeys](/0x29a-docs/introduction/hotkeys.md) and the [thread](/0x29a-docs/runtime/thread.md) reference for logic that needs to run outside the render frame.


---

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