Generated by ChalkProduction pipelineCaptions included
The water cycle, explained visually
2:07 · 1920 × 1080 · English captions
Chalk showcase
A complete generated lesson, ready to explore.
Explore a completed Chalk lesson, its accessibility features, and the system behind it. This page clearly presents a saved result rather than a new live render.
Built for learning
Explore a complete lesson Chalk already generated.
General-purpose AI video optimizes for spectacle. Educational video must preserve sequence, legibility, relationships, and timing.
Chalk turns one question into a narrated, hand-drawn lesson. Agents make the teaching decisions; a deterministic compiler enforces the visual rules.
Explore Chalk in three minutes
No account required
Public sample gallery
Generated lesson
This water-cycle lesson was generated by Chalk's production pipeline and is available here as a complete, captioned example.
What to look for
- One visual grammar per teaching idea
- Speech-timed reveals and readable labels
- A consistent illustration system and recap
Read the full water-cycle transcript
Water on Earth
Earth holds a fixed amount of water. Ninety-seven percent of this water is salty ocean water. Only three percent of Earth's water is fresh water. Only one percent of this fresh water is accessible on the surface.
Evaporation
Step one begins when the sun heats the ocean surface. Liquid water absorbs this heat and transforms into invisible gas. Eighty percent of all water vapor comes from our oceans. This warm gas rises high into the sky.
Transpiration
Step two is transpiration, where plants release water vapor. First, roots pull liquid water up from the soil. Then, leaves release this water through tiny pores. One single oak tree releases forty thousand gallons of vapor every year.
Condensation
Step three is condensation, where rising vapor cools down. The temperature drops three point five degrees Fahrenheit for every thousand feet. This cold air forces the rising vapor to clump together. The vapor turns into liquid droplets to form clouds.
Precipitation
Step four is precipitation, when clouds get too heavy with water. Gravity pulls this stored water back down to the ground. Above thirty-two degrees Fahrenheit, water falls as liquid rain. Below thirty-two degrees Fahrenheit, water freezes into snow.
Collection
Step five is collection, which divides water into two main paths. Path one is runoff, where water slides into rivers. Path two is infiltration, where water sinks deep into the soil. Both paths eventually empty back into the ocean.
Recap
Let us review the five steps of the water cycle. First, water evaporates from oceans and transpires from plants. Second, the rising vapor cools and condenses into clouds. Third, precipitation falls and collection returns it to the sea. This same water has recycled for four billion years.
Technical explanation
How Chalk works
Creative where teaching needs judgment. Deterministic where clarity needs rules.
- Plan01
Teaching agents make the lesson
Gemini agents research, outline, edit the narration, establish a visual bible, and direct every scene from one whole-video blueprint.
Research + outline + parallel scene direction
- Compile02
Typed rules protect clarity
Bounded scene JSON is sanitized and Zod-validated. TypeScript owns measured text, layout, collision repair, connectors, and speech-led timing.
Validated scene graph + deterministic geometry
- Deliver03
One render, progressive and downloadable
SVG frames are deduplicated, rasterized with Sharp, and encoded by FFmpeg into HLS, MP4, captions, and a readable transcript while Convex coordinates queue state and media.
HLS + MP4 + WebVTT + transcript
The core engineering boundary
A model can propose. Only validated data can render. This keeps the lesson flexible without giving an LLM control over final geometry, timing, or encoding.
Inside the build
What Chalk includes
Each item below describes implemented behavior or an artifact available in the repository. Provider-backed generation is the only feature currently paused.
Problem & solution
Designed for learning, not spectacle
Educational video must preserve sequence, legibility, relationships, and timing. Chalk pairs agentic teaching decisions with deterministic visual rules.
Innovation
Creative planning, deterministic presentation
A model can propose a lesson and its visual intent, but only sanitized, validated scene data can reach the renderer.
Technical achievement
A complete media pipeline
Parallel scene design, semantic icon retrieval, per-beat TTS timing, typed scene graphs, SVG/Sharp rendering, FFmpeg, HLS, and MP4 work as one system.
Architecture & scale
Long-running jobs are isolated from the web tier
Next.js serves the UI, Convex coordinates queue state and media, and outbound leased workers reject stale callbacks. Worker replica scaling is manual today.
UX & accessibility
The explanation stays usable
Responsive layouts, keyboard focus, captions, transcripts, live status, MP4 download, and accessible owner actions cover the journey around the video too.
Completion & confidence
The core workflow is implemented and tested
Deterministic tests, Convex integration tests, desktop/mobile Playwright checks, axe accessibility checks, CI, documentation, and a deployment runbook support the build.
Continue exploring
Explore a real result here, then inspect the implementation in the repository.
This showcase stays available without an active backend or cloud worker, and the saved lesson is always identified as an existing result.