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

Video generation prompt: Display a simple binary tree on a light background: node 1 is the root, with children 2 and 3; node 2's children are 4 and 5; node 3's children are 6 and 7 — all 7 nodes labeled 1-7. Use a bright color (e.g., red) to highlight nodes as they are visited during a pre-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, stepwise pre-order traversal on a fixed binary tree structure.
Minimum mechanism: Node illumination must be temporally atomic and causally bound to list digit appearance; tree topology must enforce unique preorder path; light background ensures contrast for bright-node visibility; horizontal list must be spatially anchored and incrementally populated.
(ii)Storyline: Frame 1–2: Static binary tree with all 7 labeled nodes on light background, all nodes bright-colored, output list empty. Frame 3–4: Node 1 illuminates (intensified brightness/hue), then digit "1" appears leftmost in list. Frame 5–6: Node 1 dims, node 2 illuminates, then "2" appends right of "1". Frame 7–8: Node 2 dims, node 4 illuminates, then "4" appends. Sequence continues identically for 5→3→6→7. Final frame: Full tree static, list reads "1 2 4 5 3 6 7", all nodes returned to base bright state. No camera motion; fixed frontal viewpoint; no occlusion; all transitions occur within same continuous shot.

Manual:
Experimental Procedure
1. Render a light-background scene containing a structurally correct binary tree with 7 nodes labeled 1–7.
2. Highlight all nodes in bright red (or equally saturated non-gray color).
3. Traverse nodes in preorder: illuminate node 1 → append "1" to horizontal output list at bottom; illuminate node 2 → append "2"; illuminate node 4 → append "4"; illuminate node 5 → append "5"; illuminate node 3 → append "3"; illuminate node 6 → append "6"; illuminate node 7 → append "7".
Observation of Experimental Phenomena
- Binary tree remains static with fixed node positions and connecting edges.
- Each node illuminates individually and exclusively in exact sequence 1→2→4→5→3→6→7.
- Horizontal output list grows left-to-right with digits appearing one-by-one in that same order, no omissions or rearrangements.
Summary of Experimental Principles
Preorder traversal visits root → left subtree → right subtree; for this tree, the visit order is defined by structural parent-child relationships and yields sequence 1,2,4,5,3,6,7.

Prompt Grounding rubric:
level_1: No binary tree appears at all: there are no labeled nodes 1–7, no light background, no horizontal output list, and no node ever illuminates.
level_2: A tree-like shape appears but isn't a valid binary tree (e.g., some node has more than two children, nodes are disconnected, or edges are missing); fewer than 5 distinct node labels are visible; the background is dark or patterned rather than light; or the horizontal output list is missing or contains non-numeric symbols.
level_3: A valid binary tree with exactly 7 nodes labeled 1–7 appears on a light background (each node has at most two children and all nodes are connected in a single tree); a horizontal output list appears at the bottom of the screen and contains numeric characters; at least three separate nodes illuminate at different points in the video.
level_4: All 7 nodes are present, labeled 1–7, connected in the specific structure described in the prompt (1's children are 2 and 3; 2's children are 4 and 5; 3's children are 6 and 7), shown on a light background; the horizontal output list appears at the bottom and displays digits added left to right; each of the 7 nodes illuminates individually at some point, and each illumination is followed by a digit being appended to the list, but one node's illumination might be missing, one label might be briefly hard to read during its illumination, or two illuminations might overlap in a way that looks unintentional.
level_5: All 7 nodes appear in exactly the structure described in the prompt, labeled 1–7, on a uniform light background; the horizontal output list appears continuously at the bottom and grows left to right with no gaps, deletions, unexplained insertions, or duplicate digits; each of the 7 nodes illuminates individually, one at a time, with no two nodes ever appearing illuminated at the exact same instant, and every illumination is followed by exactly one digit being appended to the list.

Scientific and Causal Correctness rubric:
level_1: There's no sign of preorder logic: nodes don't illuminate in any sequential way, the output list stays empty or shows numbers in a completely different order (e.g., 4,2,5,1,6,3,7), node colors don't consistently mark the visited node, and there's no visible link between a node illuminating and a digit appearing in the list.
level_2: Nodes illuminate, but not in an order related to preorder traversal; the output list contains digits but violates the correct sequence (e.g., 4 is skipped, 2 repeats, or an extra digit like 8 appears); at least three nodes never receive the bright highlight color; there's no visible sign that illuminating a node is what causes a digit to be appended.
level_3: Nodes are highlighted in a bright color, though at least two nodes use a noticeably dimmer or desaturated version of it; illuminating a node is followed by a digit being appended to the list, but for two or more nodes the digit doesn't match the node that just illuminated; the early part of the sequence is correct (1, then 2, then 4, then 5, then 3, matching preorder) but 6 and 7 are out of order or one of them never appears.
level_4: All nodes use the same bright highlight color when illuminated; every illumination is immediately followed by the matching digit being appended to the list; the full preorder sequence (1, 2, 4, 5, 3, 6, 7) is correct except for exactly one slip: either two adjacent digits are swapped or exactly one digit is missing even though its node illuminated.
level_5: All nodes are illuminated with the same bright, clearly visible color; every illumination event is followed immediately by the exact matching digit appearing in the output list, one digit per illumination with no flicker or overwriting; the full sequence 1, 2, 4, 5, 3, 6, 7 appears with no digit omitted, duplicated, swapped, or delayed; the link between a node lighting up and its digit appearing is clear and unambiguous throughout.

Spatiotemporal Consistency rubric:
level_1: The tree falls apart partway through: nodes jump to new spots, edges snap into different connections, or labels detach from their nodes; a node's illumination glitches or renders at a different on-screen location than that node's fixed position; the output list appears or disappears abruptly, or scrolls vertically instead of staying in its horizontal row; the background flickers or changes color or texture.
level_2: A node's position shifts noticeably between one illumination and the next (e.g., it moves by a large fraction of the screen); edges reconnect to different nodes inconsistently; more than one node stays illuminated at the same time with no fade between them; or the output list's digits jump sideways, change size, or shift alignment partway through.
level_3: Every node stays in the same spot relative to the others for the whole video; every edge stays connected and visible; each node's illumination clearly turns on and then off; the output list stays anchored at the bottom with consistent spacing, but one node briefly blinks out of view during its own illumination, one edge disappears for an instant, or one list digit briefly appears twice before settling to one.
level_4: The tree's layout never shifts: no node moves, rotates, resizes, or gets blocked from view; no edge breaks or reconnects; each illumination turns on and off cleanly with no partial or bleeding glow; list digits appear and then stay put with no jitter, sliding, or realignment; the only shortcoming allowed is something very minor and isolated, such as a single frame where one illumination's glow looks slightly mismatched, or one digit's brightness briefly dips before recovering.
level_5: Every node, edge, label, and the output list itself stay in identical position, size, and orientation across the entire video; each illumination switches on and off cleanly with a crisp edge and no trailing blur or ghost image; every appended digit uses the same font, size, spacing, and baseline as the others and stays perfectly still once it appears; no frame shows warping, stuttering, or any spatial or timing inconsistency.