Domain: Engineering — Network Engineering
Target concept: Tree Topology Network

Video generation prompt: Build a tree topology network, with the root router (red) as the first-level node, and two layer-2 switches (yellow) on the left and right as second-level nodes. Each layer-2 switch connects to three end host devices (blue), with solid lines used to connect nodes in layers. Initially, all node links are normally communicating. Disconnect the link between the left layer-2 switch and the root router, and observe the communication status of each host. Normally communicating links are indicated by green blinking.

Evaluation guide:
(i) Target concept: Network reachability in tree topologies depends on upstream path integrity.
Minimum mechanism: A layer-2 switch forwards frames only within its own broadcast domain and cannot route around a lost upstream link. In this video, green blinking on a link represents that link's role in reaching the root router, not merely whether the wire itself is plugged in. When the left switch's uplink to the root router is cut, the three hosts wired to the left switch lose their only path to the router, so blinking stops on their links too, even though their physical connection to the left switch is untouched; hosts on the right side keep their path to the router and keep blinking normally.
(ii)Storyline: Frame 0–2: Full topology displayed with all links green-blinking. Frame 3–4: Disconnection event: left uplink visibly removed or disabled. Frame 5–10: Stable post-disconnect state: blinking absent on the left uplink and on the three left-switch-to-host links; all other links retain identical green blinking; no host or switch relocates, resizes, or changes color; viewpoint remains fixed; blinking rhythm remains constant across surviving links.

Manual:
Experimental Procedure
1. Display the tree topology: red root router at top; yellow layer-2 switches left/right below it; six blue end hosts — three under the left switch, three under the right switch — all connected by solid lines.
2. Initially, all links show green blinking (representing active reachability to the root router).
3. Disconnect the solid link between the left switch and the root router.
Observation of Experimental Phenomena
- Green blinking stops on the disconnected left uplink and on the three links connecting the left switch to its own hosts, because that branch no longer has any path to the root router — even though those hosts remain physically wired to the left switch.
- Blinking continues unchanged on the right uplink and on the right switch's own links to its three hosts.
Summary of Experimental Principles
Tree topology relies on a single upstream path per switch; cutting the left switch's link to the root router removes the left subtree's only route to the rest of the network, so the video shows blinking stop on that entire branch's links, while the right subtree keeps its path to the router and keeps blinking normally.

Prompt Grounding rubric:
level_1: No red root router, no yellow layer-2 switches, or no blue end hosts appear; or the parent-child tree layout (router above two switches above six hosts) is not shown; or the left switch's uplink to the root router is never shown being disconnected.
level_2: At least one of the router, switches, or hosts appears, but they are not arranged as a router-to-two-switches-to-hosts tree; or the disconnection is shown on the wrong link (e.g., the right uplink, or a switch-to-host link) instead of the left switch's uplink to the root router.
level_3: The red root router sits at the top; the two yellow layer-2 switches sit directly below it, one on each side; six blue end hosts appear, three wired to the left switch and three to the right switch, all with solid lines; the link between the left switch and the root router is the one shown being disconnected; every node and link is clearly visible and identifiable.
level_4: Everything required for score 3 is shown, and in addition: the disconnection is visually unmistakable (the line between the left switch and the root router visibly breaks, fades out, or is removed) at that specific connection point; each switch has exactly three hosts; no extra nodes, no host-to-host or switch-to-switch links, and no third switch appear.
level_5: Everything required for score 4 is shown, and in addition: the left switch and its three hosts form a clearly grouped left side, the right switch and its three hosts form a matching right side, and the root router sits centered above both; every solid line connects a parent to its child only (no sibling-to-sibling lines); the left uplink is the only link that changes state anywhere in the video.

Scientific and Causal Correctness rubric:
level_1: No link ever shows green blinking, or every link keeps blinking including the disconnected left uplink, or the video never shows any change in which links are blinking after the disconnection.
level_2: Some links blink and some don't, but not for the right reason: for example the disconnected left uplink itself keeps blinking, or blinking stops on links that have nothing to do with the left switch, or no host's status visibly changes after the disconnection.
level_3: Every link blinks green except the disconnected left uplink and the three links from the left switch to its own hosts: those four links stop blinking because the left branch no longer has a path to the root router; the right uplink, both links from the right switch, and its three host links keep blinking normally throughout.
level_4: Everything required for score 3 holds, and in addition: blinking on the left switch's three host links stops completely (no partial or flickering blink), while every link on the right side shows no change at all in its blinking rate or brightness.
level_5: Everything required for score 4 holds, and in addition: the three left-side host links stop blinking at essentially the same moment the left uplink is disconnected (not noticeably staggered); the right-side links keep the same blink rhythm and brightness before and after the disconnection; the disconnected left uplink shows no blinking at any point afterward.

Spatiotemporal Consistency rubric:
level_1: A node (router, switch, or host) suddenly appears in a new spot or jumps into place instead of being placed normally; a node's size suddenly changes; a link suddenly stretches or shrinks; or the overall scene brightness jumps abruptly partway through.
level_2: At least one clear motion problem: the left switch slides sideways without a smooth path; hosts blink on/off at irregular, unpredictable intervals; the disconnection happens as a sudden jump-cut rather than a clean break or fade; or the background shifts or rotates.
level_3: The router, switches, and hosts all stay in the same positions relative to each other for the whole video; every node and link that belongs in the scene stays visible throughout, except that the one disconnected link is removed as expected; the blinking on every still-active link keeps a steady, even rhythm; no line or node shape warps, stretches, or jitters.
level_4: Everything required for score 3 holds, and in addition: the disconnected link either vanishes in a single frame or fades out smoothly over a couple of frames, rather than flickering in and out; every still-blinking link keeps the same on/off timing and duration as every other still-blinking link; no line or node edge appears torn or broken up.
level_5: Everything required for score 4 holds, and in addition: no link or node looks blocky, blurry, or distorted at any point; the blinking never stutters or skips a cycle on any still-active link; the background grid (if shown) and the foreground nodes don't drift relative to each other; the camera view never pans, zooms, or rotates.