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The Flow Builder is the heart of Plural — a visual canvas where you connect elements into conversation flows that your robot or avatar executes when it detects a human nearby. Understanding how flows work helps you create engaging, natural interactions from the first moment a user appears.

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How Flows Work

Every Plural project starts with two special system nodes at the top of your canvas: Human detected and No human detected.
  • When a robot or avatar detects a human (via face detection), it begins executing the flow connected to the Human detected node, following arrows from element to element.
  • When no human is in the robot’s field of view, the device loops on the No human detected node — your idle screen.
  • If a robot or avatar loses sight of a face while a flow is running, the flow immediately jumps back to the No human detected node.
NAO behaves differently from other devices. While a flow is running, NAO does not cancel it when no human is detected. You can use open-ended flows (elements with no outgoing arrow) to give NAO natural pause points where it can restart or wait for interaction. See the section below for more details.

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Awareness Feature

The Awareness Feature governs the transition between idle and active states:
  • The “No human detected” node acts as a repeating idle state — it loops as long as no human is seen.
  • As soon as a face is detected, the flow following “Human detected” triggers and runs until no human has been seen for 3 seconds.
  • Use the “No human interaction for 20 seconds” trigger on elements to prompt the robot to repeat a question or offer a hint if the user goes quiet.

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Frames

Frames are containers on the canvas that group a set of connected elements into a logical flow. Each frame is associated with a specific device type (Avatar, Pepper, Temi, or NAO).
1

Add a frame

Click the + button on the canvas or use the toolbar to add a new frame and select the device type.
2

Resize a frame

Click the frame’s border to highlight it, then drag any side or corner to resize. Frames also expand automatically when you drag elements to the edge.
3

Move a frame

Hover over the top bar of the frame until your cursor changes, then click and drag to reposition it on the canvas.
4

Delete a frame

Right-click the frame and choose Delete from the context menu, or click the robot-type icon in the upper-left corner, open the sidebar panel, and select Delete followed by confirmation.
Changing the device type of a frame after you have already added device-specific elements will fail. For example, if your Temi frame contains navigation elements, you cannot switch it to an Avatar frame because avatars cannot move.

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Flow Navigation

Use these controls to move around large canvases comfortably:
ActionHow to do it
Pan the canvasHold the left mouse button (or middle-click) and drag
Zoom in / outScroll the mouse wheel
Jump to a specific frameUse the frame selector in the top toolbar
Move a frameDrag its top bar

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Connecting Elements with Flow Arrows

Draw connections between elements by dragging the output circle on one element to another element or to an empty area (which opens the element picker). The arrow defines the sequence the robot follows.
  • Add back buttons by drawing an arrow from a later element back to an earlier one.
  • For long flows, return users to the second element at the end rather than the first to skip repeated introductions.
  • Leave no dead ends — an element with no outgoing arrow leaves the robot frozen on the last screen. Connect open ends back to a menu or the flow start.
Check out the Plural example project, the Wine Sommelier at https://go.plural.io/s/9c453bf582, to see a well-structured long-form flow in action.

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General Design Suggestions

Good flows feel like natural conversations, not monologues. Keep these principles in mind:

Keep it conversational

Avoid long introductory speeches, especially ones that repeat on every visit (like main menus). Guide users by suggesting options they can say or tap.

Give users a way out

Always provide back buttons or verbal escape routes so users can revisit content or exit gracefully.

Use media thoughtfully

When displaying images or video, give users enough time to view them. Consider hiding buttons and letting users say “next” or “back”.

Handle silence

Use the “No human interaction for 20 seconds” feature to prompt users who have gone quiet — repeat the question or offer a gentle hint.

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NAO-Specific Differences

NAO is a screenless robot with unique flow behavior. Keep these differences in mind when designing for NAO.
Unlike Pepper, Temi, and Avatar — which stop a flow when face detection is lost — NAO continues running the active flow regardless of human presence. This means:
  • Open ends are intentional — leaving an element without an outgoing arrow gives NAO a natural breakpoint where it can return to its idle state.
  • No screen — NAO cannot show visual buttons or UI panels. Every instruction must be delivered verbally. Always tell the listener what words or phrases NAO expects to hear.
  • No “No human interaction for 20 seconds” fallback is needed in the same way — use open-ended flows instead to create return-to-idle points.

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Context Menu

Right-clicking anywhere on the canvas or on a frame’s border opens the context menu, which gives you quick access to options such as adding a new frame, deleting the current frame, and other canvas-level actions.