Domain: Engineering — Network Engineering
Target concept: TCP Three-Way Handshake for Connection Establishment

Video generation prompt: An animation simulates a TCP protocol experiment, in which a client (blue) initiates a TCP connection to a server (red). Green waveforms are used to label the transmission of TCP packets between the client and the server. The screen displays the process of TCP packet transmission that successfully establishes a TCP connection between the client and the server.

Evaluation guide:
(i) Target concept: Visual causality of TCP connection establishment via ordered, directional packet exchange.
Minimum mechanism: Three discrete, unidirectional signal propagations must occur in strict sequence (SYN → SYN-ACK → ACK), each tied to a fixed-color endpoint and labeled by green waveform; no concurrent or reversed causality; no state persistence beyond packet transit.
(ii)Storyline: Frame 0–t₁: Blue client stationary, emits green waveform moving rightward to red server → SYN event. At t₁, waveform fully arrives; server remains static, no color/state change. Frame t₁–t₂: Red server emits green waveform moving leftward to blue client → SYN-ACK event. At t₂, waveform fully arrives; client remains static. Frame t₂–t₃: Blue client emits green waveform moving rightward to red server → ACK event. At t₃, waveform fully arrives; connection established. Throughout: fixed side-by-side spatial layout (client left, server right), frontal orthogonal viewpoint, no camera motion, no occlusion, no secondary agents or annotations.

Manual:
Experimental Procedure
1. Blue client emits first green waveform toward red server.
2. Red server emits second green waveform toward blue client.
3. Blue client emits third green waveform toward red server.
Observation of Experimental Phenomena
- Three green waveforms appear sequentially, each traveling between client and server.
- First waveform: blue → red.
- Second waveform: red → blue.
- Third waveform: blue → red.
- Client remains blue, server remains red, no color change occurs.
Summary of Experimental Principles
TCP three-way handshake: SYN (client→server), SYN-ACK (server→client), ACK (client→server) — establishing reliable connection before data transfer.

Prompt Grounding rubric:
level_1: No blue client or red server appears; or no green waveform is shown; or there's no sign of packets moving between the two endpoints; or no sequence of connection-establishment steps is shown at all.
level_2: The client or server appears, but its color is wrong (client isn't blue, or server isn't red); the green waveform is missing or used for something other than a packet; or the shot doesn't show any recognizable SYN / SYN-ACK / ACK sequence.
level_3: The blue client and red server both appear and stay visually distinct; green waveforms mark packet transmissions; three separate transmissions occur in this order: client-to-server, then server-to-client, then client-to-server; no other packet types (such as FIN or RST) appear.
level_4: Everything required for score 3 is shown, and in addition: the first waveform clearly starts at the client and ends at the server, the second starts at the server and ends at the client, the third starts at the client and ends at the server; every waveform shown is green and only these three packets are represented.
level_5: Everything required for score 4 is shown, and in addition: no extra nodes, duplicate waveforms, or background text/icons distract from the client, server, and waveforms; the client and server stay in the same place and the same size throughout; each of the three waveforms appears only during its own transmission and disappears right after it arrives, with no waveform lingering into the next step.

Scientific and Causal Correctness rubric:
level_1: The direction of the packets shown has no connection to real TCP logic; the colors (blue client, red server, green waveform) don't correspond to anything meaningful; or green is used for something that isn't a packet.
level_2: The client and server colors are shown but don't stay consistent (e.g., the client turns red partway through); the green waveforms don't clearly travel from one endpoint to the other; or at least one packet appears out of the correct SYN, SYN-ACK, ACK order.
level_3: The client sends the first packet (SYN) to the server; the server replies with the second packet (SYN-ACK) to the client; the client sends the third packet (ACK) to the server; all three waveforms start and end at the correct endpoints in the correct order; no packet appears to represent the wrong step (e.g., nothing looks like a SYN-ACK originating from the client).
level_4: Everything required for score 3 holds, and in addition: it's visually clear which waveform corresponds to which step (first = SYN, second = SYN-ACK, third = ACK), with no waveform suggesting two steps at once; neither the client nor the server changes color or otherwise reacts incorrectly upon receiving a packet.
level_5: Everything required for score 4 holds, and in addition: the second waveform (SYN-ACK) only starts after the first waveform (SYN) has completely reached the server; the third waveform (ACK) only starts after the second waveform has completely reached the client; no waveform begins while the previous one is still in transit, so the cause-and-effect order stays visually unambiguous.

Spatiotemporal Consistency rubric:
level_1: The client or server jumps to a new position or blinks in and out of existence; a waveform tears or fragments mid-flight; the lighting or shadows change abruptly; or the client/server shape suddenly stretches, skews, or rotates for no story reason.
level_2: The client or server changes size or orientation between frames without a smooth transition; a waveform freezes and then jumps ahead, or moves backward; a waveform starts before its source is fully drawn, or ends before it reaches its target; or something blocks the client/server on and off without a consistent reason.
level_3: The client and server stay in the same place with a stable look (no change in shape, size, or orientation); all three green waveforms travel along smooth, continuous paths from source to destination; nothing in the scene blinks out of existence and comes back mid-video; there's no sudden lighting change affecting the client or server; nothing splits apart or fractures unexpectedly.
level_4: Everything required for score 3 holds, and in addition: each waveform travels in one direction without doubling back, looping, or pausing; no waveform crosses through another waveform or through the client/server except right at its start or end point; the client and server keep the same recognizable shape, size, and color throughout, with no visible distortion or recoloring.
level_5: Everything required for score 4 holds, and in addition: the motion is fluid with no dropped frames or blur that hides where a waveform starts or ends; each waveform's leading edge keeps a consistent thickness and sharpness as it travels; the relative positions of the client, server, and waveforms stay consistent with a fixed, straight-on camera view, with no sense of the viewpoint shifting.