🟥 Once

The Once block allows you to limit the execution of a flow to a single occurrence, acting as a logical "gate" (DoOnce/Gate). It blocks subsequent passages after first use, while providing controls to reset its state.

This block is ideal for preventing unwanted repetitions (e.g. multiple triggering of a trap) or guaranteeing the uniqueness of an action (e.g. distribution of a reward).

📥 Entries

• in (Flow): Input flow to execute if the block is open. Once passed, the block closes automatically.
• open (Control flow): Forces the block to open, allowing the in flow to pass again.
• close (Control flow): Forces the block to close, blocking any further passage.
• toggle (Control flow): Inverts the current state of the block (open → closed / closed → open).
• closed (Boolean): Initial state of the block upon loading (True = closed, False = open by default).

📤 Outings

• out (Flow): Output flow activated only if the block was open when in was triggered.

💡 Example of use

Scenario: Single-use emergency button

1. A red “Alert” button is placed in a level.
2. Clicking on this button is connected to the in input of the Once block (set to closed = False).
3. The out output triggers an audible alarm and sends a message to the guards.
4. The player presses once: the alarm goes off, and the block closes automatically.
5. The player presses again: nothing happens, because the block is now closed.
6. To reset the button (e.g. after a level reset), a stream is connected to the open input.

⚙️ Technical Details

• Internal behavior: The block maintains a persistent closed state. Triggering in toggles this state from open to closed by default.
• Priority management: The open, close and toggle entries take precedence over the current state and can modify it at any time.

Updated on: 04/03/2026