Domain: Engineering — Electrical Engineering
Target concept: The brightness of the LED is updated by the microcontroller at different fixed time intervals.

Video generation prompt: On the workbench, a microcontroller drives two identical LEDs mounted side by side; as a knob is turned, the control signal reaching the LEDs changes, and the brightness of each LED updates over the course of the clip.

Evaluation guide:
(i) Target concept: Fixed-interval digital PWM control of LED brightness via analog knob input, implemented with asymmetric timing for two parallel outputs.
Minimum mechanism: Microcontroller must sample knob position periodically, map it to duty cycle, and independently trigger brightness updates for each LED on separate fixed timers — no shared clock or synchronization between left/right update events.
(ii)Storyline: [Start] Static setup: workbench with microcontroller, side-by-side LEDs, knob at initial position. → [Action onset] Knob begins smooth unidirectional rotation. → [Causal transition 1] Left LED emits first brightness step; right LED emits first brightness step at visibly shorter delay. → [Causal transition 2] Right LED emits second brightness step while left LED remains unchanged. → [Causal transition 3] Left LED emits second brightness step only after multiple right LED steps. → [Continuation] Pattern repeats with fixed left:right step ratio until knob stops. → [Visibility constraint] Fixed frontal camera angle; no occlusion; all components fully in frame; lighting reveals LED glow contrast and knob rotation clearly.

Manual:
Experimental Procedure
1. Place microcontroller on workbench with two identical LEDs mounted side-by-side: left LED and right LED.
2. Connect knob to microcontroller input; rotate knob continuously during recording.
3. Power system so LEDs illuminate and respond to knob rotation.
Observation of Experimental Phenomena
Left LED brightness updates at visibly slower discrete intervals; right LED brightness updates at visibly faster discrete intervals; both update only while knob rotates; intervals are regular and distinct.
Summary of Experimental Principles
The brightness of the LED is updated by the microcontroller at different fixed time intervals.

Prompt Grounding rubric:
level_1: No workbench, microcontroller, knob, or LEDs are visible; or only one LED is shown; or the two LEDs do not match each other in size, shape, color, or mounting; or the two LEDs are stacked one above the other instead of sitting beside each other.
level_2: The workbench and knob are visible and two identical LEDs sit beside each other, but the microcontroller itself cannot be identified in the shot; or the knob never visibly turns during the clip; or one LED is missing or has been replaced by something else.
level_3: The workbench, a microcontroller, a knob, and two identical LEDs mounted beside each other are all visible; the knob visibly rotates at some point during the recording; both LEDs are lit at some point in the clip; neither LED disappears or gets swapped for something else mid-clip.
level_4: Everything required at the 3-point level holds, and in addition the left LED and right LED stay clearly identifiable as left and right from the fixed camera framing; brightness changes in either LED occur only while the knob is turning, never while it sits still; nothing in the frame blocks the view of either LED or the knob.
level_5: Everything required at the 4-point level holds, and in addition the two LEDs match each other in mounting, size, and orientation for the whole clip; the knob turns smoothly in one direction without reversing or jittering back and forth; both LEDs stay visible the entire time without dropping out of frame; and neither the LEDs nor the knob show visual glitches such as doubled edges or clipped shapes.

Scientific and Causal Correctness rubric:
level_1: Neither LED changes brightness at all; or both LEDs change brightness at exactly the same moments every time; or a brightness change happens while the knob is not moving; or one LED stays constantly on or constantly off with no variation while the other one changes.
level_2: Both LEDs do change brightness, but at rates a viewer cannot tell apart (neither one clearly updates more often than the other); or the brightness changes look random rather than following a repeating, evenly spaced pattern; or an LED changes once and then stays put for an unusually long stretch that breaks the sense of a fixed update rate.
level_3: The left LED visibly changes brightness less often than the right LED over the course of the clip; both LEDs jump between brightness levels rather than fading smoothly from one level to the next; every brightness change in either LED happens only while the knob is turning.
level_4: Everything required at the 3-point level holds, and in addition the gaps between the left LED's brightness changes stay visibly longer and more even than the gaps between the right LED's brightness changes, across the whole clip rather than just at the start.
level_5: Everything required at the 4-point level holds, and in addition the right LED updates noticeably faster than the left LED throughout the clip - roughly twice as often or more, for example cycling through four brightness steps while the left LED completes only one - not just briefly at the beginning; and each brightness change lines up with a moment when the knob's position is visibly moving, rather than appearing with no matching knob movement.

Spatiotemporal Consistency rubric:
level_1: An LED, the knob, or the microcontroller drops out of the shot for a moment and then reappears; either LED jumps to a different spot on the workbench without visibly moving there; the ambient lighting suddenly switches between bright and dark with no lamp, switch, or cause shown; an LED's shape stretches, warps, or fractures between frames; the workbench surface itself changes shape or texture between frames; or the camera cuts to a different framing partway through the clip.
level_2: The knob's rotation axis shifts sideways or wobbles as though it were not fixed in place; one LED's position drifts slightly across frames for no mechanical reason; the shadow cast by the knob or an LED flips direction abruptly with no change in lighting shown; or an LED's outline briefly doubles or smears in a way that doesn't match an actual brightness change.
level_3: The workbench, microcontroller, knob, and both LEDs keep sitting in the same positions relative to one another for the whole clip; neither LED drops out of frame at any point; neither an LED nor the knob changes shape or stretches between frames; the knob's mount and the LEDs' housings show no sudden break in appearance.
level_4: Everything required at the 3-point level holds, and in addition the knob rotates only about its own fixed center, with no sideways sliding while it turns; each LED's brightness change appears as a clean transition rather than a frozen or skipped frame; the LEDs' housings and mounting hardware line up from frame to frame with no visible misalignment.
level_5: Everything required at the 4-point level holds, and in addition the background behind the workbench stays put with no drifting or floating, consistent with a camera that never moves; each LED's glow keeps a similar halo size and softness across its different brightness levels; the knob's turning speed looks even, without sudden speed-ups or stalls; and no stray flicker appears in either LED except at its own brightness-change moments.