Domain: Engineering — Computer Science
Target concept: Binary Tree Postorder Traversal Demonstration

Video generation prompt: Display a simple binary tree with marked nodes (1–7) on a light background: 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 (e.g., red) to highlight the nodes to demonstrate post-order traversal. Whenever a node is visited, briefly illuminate it and append its value to the horizontal output list at the bottom of the screen in left-to-right order.

Evaluation guide:
(i) Target concept: Visual demonstration of deterministic, sequential node visitation governed by post-order tree traversal logic.
Minimum mechanism: Each node must be uniquely identifiable by label and position; illumination must serve as unambiguous temporal marker of visitation; list append must be causally bound to illumination onset; spatial layout must preserve parent-child hierarchy to support structural reasoning.
(ii)Storyline: Frame 1–2: Static binary tree (7 nodes, light background, red labels) fully visible. Frame 3–4: Node 4 illuminates → “4” appears at leftmost position of bottom list. Frame 5–6: Node 5 illuminates → “5” appends right of “4”. Frame 7–8: Node 2 illuminates → “2” appends right of “5”. Frame 9–10: Node 6 illuminates → “6” appends. Frame 11–12: Node 7 illuminates → “7” appends. Frame 13–14: Node 3 illuminates → “3” appends. Frame 15–16: Node 1 illuminates → “1” appends. Final frame: Full list “4 5 2 6 7 3 1” visible; all nodes dimmed except final illumination fading. Perspective: Fixed front-facing 2D view; no camera motion; all elements fully in frame; no occlusion.

Manual:
Experimental Procedure
1. Display static binary tree with 7 nodes labeled 1–7 on light background; root=1, left=2, right=3, 2→4,5, 3→6,7.
2. Highlight all nodes in bright red.
3. Traverse in post-order: illuminate node 4 → append “4”; illuminate node 5 → append “5”; illuminate node 2 → append “2”; illuminate node 6 → append “6”; illuminate node 7 → append “7”; illuminate node 3 → append “3”; illuminate node 1 → append “1”.
Observation of Experimental Phenomena
- Tree remains fixed; only one node illuminates at a time; illumination is smooth and localized.
- Output list grows left-to-right with values “4”, “5”, “2”, “6”, “7”, “3”, “1” in that exact order.
Summary of Experimental Principles
Postorder traversal visits left subtree, then right subtree, then root — producing sequence: leaves first (4,5,6,7), then internal nodes (2,3), then root (1).

Prompt Grounding rubric:
level_1: No binary tree appears; nodes are not labeled 1 through 7; there's no horizontal output list at the bottom; nodes are not highlighted in bright red; no illumination effect occurs when a node is visited; the background is not light.
level_2: A tree-like diagram appears but breaks binary-tree structure (e.g., a node with three children, or unbalanced/missing branches); fewer than 7 nodes are present or their labels are missing/misplaced; the output list is absent or contains clearly wrong content (e.g., letters, blanks); red highlighting is absent or applied to things other than the nodes; no illumination effect ever occurs.
level_3: A valid binary tree with 7 nodes labeled 1 through 7 (root=1, 2 and 3 as its children, 4/5 under 2, 6/7 under 3) sits on a light background; the nodes are colored red; a horizontal output list is present at the bottom; nodes illuminate one at a time as the demonstration proceeds and the list gains entries, but the illumination-to-append linkage looks inconsistent (e.g., a node stays lit after its value is appended, or two nodes are lit at once).
level_4: Everything required at level 3 is present, and additionally, exactly one node is illuminated at a time, all 7 nodes end up red and legible, and the output list ends up containing exactly 7 entries with no gaps, but one non-core flaw remains, e.g., one node's illumination flickers or cuts out mid-glow, or the parent-child alignment on screen looks slightly off (a parent not centered above its children) even though the connections are still clear.
level_5: Everything required at level 4 is present with no remaining flaws: all 7 nodes sit in the specified parent-child layout (root=1, 2 and 3 as its children, 4/5 under 2, 6/7 under 3) and are uniformly bright red and legible; each node illuminates exactly once, only during its own visit, with a smooth onset and offset and no overlap with any other node's illumination; the output list appends exactly one new entry per illumination event with no deletions or reordering; all node labels and list text stay legible throughout.

Scientific and Causal Correctness rubric:
level_1: The visit order contradicts post-order logic (e.g., the root, node 1, illuminates before its children's subtrees finish, or the left/right subtree order is swapped); node positions don't match the intended tree (e.g., node 1 shown as a leaf instead of the root); 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 a disconnected node); the list order is nowhere close to post-order (e.g., reads 1,2,3,4,5,6,7 or some other unrelated order); node 1 (the root) illuminates first instead of last; at least three of the node illuminations have no matching list append.
level_3: The tree structure is valid, all 7 nodes illuminate exactly once, and the output list contains all 7 numbers, but the list's order is a different traversal (e.g., preorder 1,2,4,5,3,6,7 or inorder 4,2,5,1,6,3,7) rather than postorder 4,5,2,6,7,3,1; or for two or more nodes, the illumination timing doesn't line up with when that node's value gets appended.
level_4: Illumination consistently comes at or before its node's value is appended, and the final list order is exactly 4,5,2,6,7,3,1 with all 7 nodes correctly placed in the root=1 / children=2,3 / grandchildren=4,5,6,7 structure, but one causal link is off, e.g., node 4's value appears in the list slightly before node 4 finishes illuminating.
level_5: For every node, its illumination begins at or before its value is appended and ends at or after the append finishes; no node illuminates outside its designated turn; the list reads exactly 4,5,2,6,7,3,1; the parent-child layout is fully correct (2 and 3 under 1; 4 and 5 under 2; 6 and 7 under 3); and no stray illumination or extra list entry contradicts postorder logic anywhere in the sequence.

Spatiotemporal Consistency rubric:
level_1: Nodes jump to new positions between frames, an edge disappears and reconnects to a different node, the whole tree vanishes and reappears, a node's illumination blinks on and off more than twice in a row, or the output list gets erased 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 non-adjacent nodes illuminate at the same time, a list entry gets overwritten rather than the list simply extending, the camera pans or zooms during the sequence, or a node's brightness changes for no visible reason.
level_3: All 7 nodes stay in place throughout, every edge stays connected, only one node is illuminated at any moment, and the list grows left-to-right without deleting or reordering earlier entries, but one small timing glitch remains, such as one node snapping straight from fully lit to fully dark with no fade, or one list entry sliding in with a visible stutter.
level_4: Node positions, edges, and the background all stay completely stable, each illumination fades in and out smoothly rather than cutting abruptly, and list entries slide in from the right with even spacing and timing, but one minor flaw remains, such as one node's fade-out slightly overlapping the next node's fade-in, or the list shifting vertically by a hair while a new entry is added.
level_5: No node ever shifts position or size across the whole sequence, no edge ever distorts or disconnects, each node's illumination brightens smoothly to full, holds steady, then dims smoothly with zero overlap or bleed into neighboring nodes, the output list stays anchored at the bottom of the screen with new entries only ever appearing at its right edge in matching font and spacing, and the camera holds one fixed front-facing framing throughout with no rotation, zoom, or lighting change.