Four-stroke engine interactive explainer
We wrote these prompts and ran each one once, identically, on Gemini 4 Hydrogen, Gemini 3.8 Flash, and Gemma 4 31B through the Gemini API free tier on 14 November 2026 (America/Denver). Hydrogen and 3.8 Flash used thinking_level=MEDIUM; Gemma 4 has no thinking level. We did not edit the models’ code. Playable frames show the raw HTML or SVG (Three.js CDN URLs were rewritten to a local copy so the iframe does not call the public internet). Dollar figures are equivalent paid-tier list prices — labelled “equivalent paid cost; ran on free tier.” A 429 or quota error stops that model for the rest of the batch; leftover tests wait until the free-tier quota resets at midnight Pacific. Free-tier prompts may be used by Google to improve products. This is not a benchmark: one run per prompt, our tasks, our settings.
The prompt (copyable)
Write a single self-contained HTML page that interactively explains how a four-stroke engine works. Show a labeled animated cross-section of the intake, compression, power, and exhaust strokes. The viewer must be able to pause, step one stroke, and change a simple RPM or speed control. Include a short plain-language caption for each stroke. No external CSS, JavaScript, fonts, or images; use vanilla JS with SVG or canvas. Return only the HTML document, starting with <!DOCTYPE html>.
Side-by-side playable results
Each frame is sandboxed (scripts allowed, no same-origin). External network is blocked by CSP, except our local Three.js copy where needed.
Gemini 4 Hydrogen
ran1m 5s · 12,783 tokens · $0.0951 equiv. paid cost; ran on free tier
maxOutputTokens=24576 · thinking_level=MEDIUM
Loads a labeled four-stroke engine cross-section with Pause, Step 1 Stroke, an Engine Speed / RPM control, and a caption for each stroke. On load it was on the power stroke (stroke 3 of 4), with the piston, valves, and crankshaft drawn and labeled.
Gemini 3.8 Flash
errorThe API returned an error, including after one extra attempt. No output this session.
HTTP 503
No output this session. The Gemini 3.8 Flash API returned HTTP 503 (“high demand”) or dropped the connection. We tried once more after the first failure and did not retry in a loop. This was not a quota / 429 error.
Gemma 4 31B
errorThe API returned an error, including after one extra attempt. No output this session.
HTTP 500
No output this session. The API returned HTTP 500 (“Internal error encountered”) on the first call and again on a single later attempt, each in under a second. This was not a 429 / quota error.
Metrics
| Model | Status | Wall time | Input | Thinking | Output | Equiv. paid cost | Finish |
|---|---|---|---|---|---|---|---|
| Gemini 4 Hydrogen | ran | 1m 5s | 133 | 2,378 | 10,272 | $0.0951 * | STOP |
| Gemini 3.8 Flash | error | — | — | — | — | — | — |
| Gemma 4 31B | error | — | — | — | — | — | — |
* Equivalent paid cost; ran on free tier. Hydrogen $1.50 / $7.50 per 1M; 3.8 Flash $0.75 / $3.75 per 1M through 31 Dec 2026; Gemma listed free ($0.00). Output price includes thinking tokens.
What we observed
- Gemini 4 Hydrogen: Loads a labeled four-stroke engine cross-section with Pause, Step 1 Stroke, an Engine Speed / RPM control, and a caption for each stroke. On load it was on the power stroke (stroke 3 of 4), with the piston, valves, and crankshaft drawn and labeled.
- Gemini 3.8 Flash: No output this session. The Gemini 3.8 Flash API returned HTTP 503 (“high demand”) or dropped the connection. We tried once more after the first failure and did not retry in a loop. This was not a quota / 429 error.
- Gemma 4 31B: No output this session. The API returned HTTP 500 (“Internal error encountered”) on the first call and again on a single later attempt, each in under a second. This was not a 429 / quota error.
Observed facts only; we did not score the models and we did not fix their code.