Animate a working four-cylinder engine

# Make a 4-cylinder engine in operation

## What to make
- Rotation animation of a 4-cylinder engine model
- Sequentially show the 4 stages: intake, compression, explosion, exhaust
- Show the ignition timing of the four cylinders differently from each other
- Make the engine casing semi-transparent to visualize the internal structure
- Playback speed control
- Pause function
- Display the current operating stage (text or visual marker)
- Display the currently active cylinder
- Format accessible via a single web link (HTML/interactive web page)
- Able to run smoothly without stuttering in a laptop browser
- 1 full-cycle recorded video, 1 minute (reference video for observation)

## Evaluation criteria
- Do the four stages (intake, compression, explosion, exhaust) move in order?
- Are the four cylinders' ignition sequences offset from one another?
- Can speed be adjusted or stopped?
- Is the current stage shown on screen?
- Does it open with one link and run on a laptop without stuttering?

## Client's original text
> Make something that shows how a 4-cylinder engine runs. I'll use it on an auto maintenance channel.
> The four stages (intake, compression, explosion, exhaust) have to actually move. Not still images.
> Make it so I can slow it down or pause it to look. Also show which cylinder is in which stage right now.
> Make the outer shell semi-transparent so the inside is visible.
> It should open with one link, and a 1-minute recorded video of one full rotation.