Domain: Engineering — Computer Science
Target concept: Inorder Traversal Demonstration of a Binary Tree

Video generation prompt: Display a simple binary tree on a light background, with 7 nodes labeled 1–7: node 1 is the root, node 2 is its left child and node 3 is its right child, node 4 is 2's left child and node 5 is 2's right child, node 6 is 3's left child and node 7 is 3's right child. Use bright colors (such as red) to highlight the nodes to demonstrate in-order traversal. Whenever a node is visited, briefly illuminate it, and append its value to a horizontal output list at the bottom of the screen in left-to-right order.

Evaluation guide:
(i) Target concept: Visual demonstration of deterministic node visit order in binary tree in-order traversal via synchronized illumination and list accumulation.
Minimum mechanism: Tree must be statically laid out with fixed parent-child adjacency; illumination must be a discrete, exclusive, transient visual marker tied to visit event; list must grow additively without replacement or reordering; all labels must be unambiguously bound to their structural roles.
(ii)Storyline: Frame 1–2: Static binary tree (7 nodes, light background) fully visible, unlabeled list empty. Frame 3–4: Node 4 illuminates bright red → list shows "4". Frame 5–6: Node 4 de-illuminates, node 2 illuminates → list shows "4 2". Frame 7–8: Node 2 de-illuminates, node 5 illuminates → list shows "4 2 5". Frame 9–10: Node 5 de-illuminates, node 1 illuminates → list shows "4 2 5 1". Frame 11–12: Node 1 de-illuminates, node 6 illuminates → list shows "4 2 5 1 6". Frame 13–14: Node 6 de-illuminates, node 3 illuminates → list shows "4 2 5 1 6 3". Frame 15–16: Node 3 de-illuminates, node 7 illuminates → list shows "4 2 5 1 6 3 7". Throughout: fixed front-view camera, no motion except illumination state change; all nodes and edges remain static and fully visible; no occlusion; list updates occur only upon illumination onset and never overwrite prior entries.

Manual:
Experimental Procedure
1. Display a rooted binary tree with 7 nodes labeled 1–7: root=1, left child=2, right child=3; 2’s left=4, 2’s right=5; 3’s left=6, 3’s right=7. All on uniform light background.
2. Begin in-order traversal: illuminate node 4 → illuminate node 2 → illuminate node 5 → illuminate node 1 → illuminate node 6 → illuminate node 3 → illuminate node 7.
3. Each time a node illuminates, append its numeral to a horizontal output list at the bottom, left-to-right.
Observation of Experimental Phenomena
- Exactly 7 circular nodes, labeled 1–7, arranged in canonical binary tree topology.
- Bright red illumination appears on one node at a time, in order: 4,2,5,1,6,3,7.
- Horizontal output list at screen bottom grows sequentially: "4", "4 2", "4 2 5", ..., ending as "4 2 5 1 6 3 7".
Summary of Experimental Principles
In-order traversal visits nodes in left-subtree → root → right-subtree order, producing sorted output for BSTs; here it demonstrates structural visit sequence independent of value ordering.

Prompt Grounding rubric:
level_1: No binary tree appears; nodes are not labeled with the numbers 1 through 7; the background is not light; no horizontal list appears at the bottom of the screen; no node ever illuminates.
level_2: A tree-like diagram appears but breaks binary-tree structure (e.g., a node has more than two children, or nodes are disconnected); fewer than 7 nodes are labeled, or labels are not the numerals 1–7; the light background is missing or heavily obscured; the output list is missing or shows non-numeric content.
level_3: A valid binary tree with exactly 7 nodes labeled 1 through 7 (root=1, 2 as its left child, 3 as its right child, 4/5 as 2's children, 6/7 as 3's children) is shown on a light background; a horizontal output list is present at the bottom of the screen; nodes illuminate one at a time as the demonstration proceeds, and the list grows with numeric entries, but the illumination-to-append linkage looks inconsistent (e.g., a node stays lit while a different value is appended, or two nodes appear lit at once).
level_4: Everything required at level 3 is present, and additionally, exactly one node is illuminated at a time (never two simultaneously), each illumination clearly precedes its own value being appended to the list, and the list only ever adds entries to the right end without deleting or rewriting earlier entries, but one non-core flaw remains, e.g., the illumination color is yellow rather than the bright red called for, or one node's label sits slightly off-center though still legible.
level_5: Everything required at level 4 is present with no remaining flaws: all 7 nodes are laid out in the specified parent-child structure (root=1, 2 and 3 as its children, 4/5 under 2, 6/7 under 3) and are clearly legible; the light background is uniform and non-distracting; each node illuminates briefly and exclusively in bright red with no lingering glow; the output list at the bottom appends exactly one new value per illumination event, left-to-right, with no gaps, duplicate entries, or omissions; all labels, illumination, and list text remain simultaneously legible throughout.

Scientific and Causal Correctness rubric:
level_1: The visit order shown contradicts in-order logic (e.g., the root illuminates before its left subtree, or root-first/level-order visiting is used instead); node labels mismatch the tree topology (e.g., node 4 placed as a child of 3 instead of 2); illumination lands on nodes that were never visited, or skips nodes that should be visited; the output list contains duplicate values, missing values, or numbers outside 1–7.
level_2: The tree structure itself isn't a valid binary tree (a node with three children, or an orphaned node); the in-order sequence is entirely wrong (e.g., the list reads 1,2,3,4,5,6,7); illumination occurs on nodes out of in-order sequence (e.g., the root illuminates first); the output list contains values absent from the tree or omits two or more values.
level_3: The tree structure is valid, and the visit sequence follows the left-subtree, then root, then right-subtree pattern, but the output list appends values in plain numerical order (1–7) instead of the correct structural in-order sequence (4,2,5,1,6,3,7); or illumination lands on the correct nodes but lingers across multiple visits or spills onto neighboring nodes.
level_4: Illumination and list append consistently follow the left-root-right recursive descent, and all 7 values appear in the list in correct in-order sequence, but one causal link is weakened, e.g., the root (node 1) illuminates before its left subtree (4,2,5) has fully finished appending, or two values get appended at the same instant.
level_5: For every node, illumination happens exactly when that node is next in the canonical in-order path, with no node illuminating early, late, or being skipped; each illumination event causes exactly one list append, strictly left-to-right, matching the illumination order precisely; the final list reads 4,2,5,1,6,3,7 with no deviation; every node position respects its parent-child relationship (4 and 5 both children of 2; 6 and 7 both children of 3) with no contradiction between labels and connections.

Spatiotemporal Consistency rubric:
level_1: The tree's nodes jump to new positions between frames, an edge disappears then reconnects to a different node, the whole tree vanishes and reappears, a node or edge deforms in a way real geometry couldn't (e.g., an edge stretching to an impossible length or a node splitting into two), the background suddenly changes color or texture, a node's illumination flashes on and off more than twice in rapid succession, or the output list is wiped and rewritten instead of growing.
level_2: A node sits in a slightly different spot when illuminated than when idle, an edge briefly drops out and reappears without cause, two or more nodes appear illuminated at once without any adjacency between them, a list entry gets overwritten instead of the list simply growing to the right, the camera rotates or zooms in on the tree, or a node's brightness or highlight color changes for no visible reason.
level_3: All 7 nodes stay fixed in place throughout, every edge stays continuously connected, the background stays static with no change in color or texture, only one node is illuminated at a time, and the output list grows left-to-right without deleting or rearranging earlier entries, but one small timing flaw remains, such as a node's illumination beginning a beat after its value is appended, or one list entry appearing before its node has finished illuminating.
level_4: The tree's layout stays perfectly fixed (no node moves, resizes, or gets hidden), every edge stays taut and visible, each node's illumination turns fully on and then fully off in one clean transition, and list entries appear one at a time with even spacing and alignment, but one minor flaw remains, such as one node's illumination still fading out as the next node's illumination begins, or one list entry blurring briefly as it appears before settling.
level_5: No node ever shifts position, changes size, or changes orientation across the whole sequence; every edge stays stable and fully visible; each node's illumination turns on crisply and off cleanly with no overlap between consecutive nodes' illumination and no lingering glow; list entries appear fully formed one at a time in matching font and size, only ever extending the list to the right; the background stays a uniform light color with no flicker; and the camera holds one fixed, front-facing framing with no zoom or angle change.