Explain the Step the Learner Actually Wrote

The short answer: When a learner misses a step, Golpo can turn the correction into a short video that shows the broken line, why it fails, and the repaired step beside it. The instructor can cover that misconception without starting another screen recording.

Why this is practical now: A tutor can scale the feeling of pointing at the exact mistake. Golpo draws the diagnosis, narrates it warmly, and syncs the correction to the voice. A different mistake can become a different finished lesson.

The teacher can still be present. A selfie puts them beside the board, their own audio can carry the explanation, and a voice clone can keep later corrections recognizably theirs. One person can answer the misconceptions a cohort actually makes.

Use the full Golpo production system

Golpo is built to be the world's best AI whiteboard explainer video maker. Give it a topic, a prompt, a script, an audio recording, or a source document. It scripts, plans the scenes, designs the visuals, narrates, times and synchronizes every frame, and returns a polished video. One person can run that system across a whole course.

For wrong-step diagnosis, keep the learner's line and the corrected line on the whiteboard. A teacher presenter can deliver the opening reassurance, but the correction itself should remain visible and editable.

• Start with an idea or source. Golpo can draft the script and plan the scenes from a topic, a document, or your outline. Script Mode can also speak the exact words you already trust.
• Keep the creator present. With AI Presenter, a course creator, founder, professor, or YouTuber can upload a selfie and appear beside the whiteboard. One person can lead a large lesson library without recording every visual sequence on camera.
• Use the right voice. Own Narration turns uploaded or live-recorded audio into the visual lesson. An authorized Voice Clone gives recurring lessons a recognizable voice at scale. Consent and pronunciation review remain required.
• Repair instead of restarting. The frame-by-frame editor can replace text, images, references, or an individual visual when the QA pass finds a local problem.
• Automate at scale. The Golpo API can be called from Codex, Claude Code, or through the Golpo MCP server in Cursor, VS Code with GitHub Copilot, Claude Code, Claude Desktop, and Visual Studio. The course platform can generate, poll, review, and publish without a person moving files between tools.

Three neighboring jobs, kept apart

The Explain This button, including the job ID and the private render, is the API spoke. A walkthrough that starts from a blank exercise, with no wrong line on the table, is the exercise spoke. Pasting one exam question and producing one video, without this diagnosis pattern, is the exam-question guide. This page owns the teaching move: quote the erroneous step, break it with a substitution, then repair it.

The hub still applies. The diagnosis is not assigned until the recomputation passes and someone has watched the file.

How a submission becomes a script

1. Store the line exactly. The platform keeps the equation and the learner’s next line as text, not as a paraphrase. “They forgot to subtract” is a later sentence. The record starts with 2x = 20 or 2x + 3 = 16.
2. Draft the break. The creator agent writes a script that shows the learner’s value failing the original equation, then shows the corrected value succeeding. It may explain the legal move. It may not skip the failure.
3. Substitute independently. The QA agent plugs the numbers in again. It does not ask the draft whether the draft feels consistent. Two plugs are required: the learner’s candidate and the corrected candidate.
4. Reject a script that only shows the right answer. If the learner’s line never appears, the attempt is the wrong product. Send it back before generate.
5. Render and watch. Golpo draws the approved words. The watch-back confirms the learner’s equation and the corrected equation are not swapped on screen.

The +6 that disappeared

Constructed work: the equation is 2x + 6 = 20. The learner wrote 2x = 20 and then x = 10. They subtracted 6 from the right side only, or they dropped the term. The legal move subtracts 6 from both sides: 2x = 14, so x = 7. Check the original equation. 2(7) + 6 = 14 + 6 = 20. The learner’s value: 2(10) + 6 = 20 + 6 = 26, which is not 20.

A script that says “the answer is 7” and never shows 26 has not explained the step they wrote. The QA agent should fail that draft even though 7 is correct. Correctness of the final number is not the whole release test. Presence of the broken substitution is part of the test.

The 3 that never entered the parentheses

Constructed work: 2(x + 3) = 16. The learner wrote 2x + 3 = 16 and then x = 6.5. They distributed the 2 onto x and left the 3 alone. Expanding legally gives 2x + 6 = 16, then 2x = 10, then x = 5. Check: 2(5 + 3) = 2(8) = 16. Their value: 2(6.5 + 3) = 2(9.5) = 19, which is not 16.

The picture has to show the 2 multiplying both terms inside the parentheses. A frame that jumps from the original equation to x = 5 hides the exact mistake the lesson exists to name. 6.5 can be spoken as six and a half if the labels still show 6.5, and both forms have to denote the same number. The watch-back compares them.

These two errors are a pair the course can assign on different days. The first is an unbalanced move on a sum. The second is a partial distribution. Teaching them in one breathless minute blurs which line failed. Two lessons, two records, two checks.

Own Narration: OFF · Script Mode: ON · Duration: 1 minute · Orientation: Horizontal (16:9) · Style: Dry Erase · Color: ON · Language: English · Voice: Female 1 · Pace: Normal · Music: None

Start from the line the learner actually wrote. The equation was two x plus six equals twenty. The learner subtracted nothing and wrote two x equals twenty, then x equals ten. The six disappeared. Subtract six from both sides. Two x plus six minus six equals twenty minus six. Two x equals fourteen. Divide by two. x equals seven. Check the original equation. Two times seven plus six is fourteen plus six, which is twenty. Their value does not survive the same check. Two times ten plus six is twenty plus six, which is twenty six. Twenty six is not twenty. The first wrong step was dropping the six before dividing. Put that six back on both sides, then divide. Ten was the result of skipping a term, not the solution. Show the learner's line beside the repaired line. Twenty and twenty six should both stay visible.

The learner's line drops the six. Subtract six from both sides to reach x equals seven. Their ten produces twenty six. Show twenty and twenty six together at the end. Allowed labels: 2x + 6 = 20; Learner: 2x = 20, x = 10; Repair: 2x = 14, x = 7; Check: 2(7) + 6 = 20; Learner check: 2(10) + 6 = 26. Do not add a sample stamp, a demo label, or any claim that the lesson is fictional. Show only the labels listed. If a number appears, it must match the narration exactly. No extra dates, prices, percentages, logos, or quotations.

Diagnostic and calm. Keep the learner's line visible while you repair it.

Own Narration: OFF · Script Mode: ON · Duration: 1 minute · Orientation: Horizontal (16:9) · Style: Dry Erase · Color: ON · Language: English · Voice: Male 2 · Pace: Normal · Music: None

The equation is two times the quantity x plus three equals sixteen. The learner wrote two x plus three equals sixteen, then x equals six point five. The three never entered the parentheses. Expand first. Two times x plus two times three is two x plus six. Two x plus six equals sixteen. Subtract six. Two x equals ten. x equals five. Check the original. Two times the quantity five plus three is two times eight, which is sixteen. Their value fails. Two times the quantity six point five plus three is two times nine point five, which is nineteen. Nineteen is not sixteen. The three had to be multiplied by two. Adding it once left the left side short. The check is what makes that shortfall visible. Keep six point five and five on the screen together. Sixteen and nineteen should both stay visible.

The learner adds three once. Expand to two x plus six, then x equals five. Their six point five produces nineteen. Keep five and six point five on the last frame, with sixteen and nineteen. Allowed labels: 2(x + 3) = 16; Learner: 2x + 3 = 16, x = 6.5; Repair: 2x + 6 = 16, x = 5; Check: 2(5 + 3) = 16; Learner check: 2(6.5 + 3) = 19. Do not add a sample stamp, a demo label, or any claim that the lesson is fictional. Show only the labels listed. If a number appears, it must match the narration exactly. No extra dates, prices, percentages, logos, or quotations.

Diagnostic. Slow on six point five and on nineteen.

What the instructor queue is for

• The recomputed check does not yield 20 or 16 for the corrected value.
• The learner’s value accidentally satisfies the original equation, which means the stored “wrong line” may not be wrong. A person should look before the course scolds a correct step.
• The video draws x = 10 as the correction, or draws x = 7 as the learner’s answer.
• Generation fails. The platform keeps the submission and the job ID and does not auto-render a generic solution.

A generic solution can still exist in the exercise library. It must not be swapped in under the learner’s attempt ID. The attempt ID means “this line.” Replacing it with a blank-page walkthrough breaks the promise.

Risks

Diagnosis can overfit. The learner might have meant a different error than the one the script names, especially if the submission is only the final number. When the platform has only x = 10 and not the middle line, the QA agent should mark the diagnosis uncertain. Uncertain goes to an instructor. Guessing a story about the student’s thinking and rendering it as fact is a bad use of a fast draw.

There is also a privacy limit this guide will not paper over. A video that quotes a learner’s work should stay inside the course’s own access rules. Golpo’s render of an approved script is not a decision about who else may watch that attempt. The studio or the school decides. The second example on the API spoke is the stricter version of that hold.

When the platform should refuse to film

A diagnosis is only as specific as the stored line. Consider a constructed submission that contains only “x = 10” on the item 2x + 6 = 20. Ten is wrong, and several stories could produce it: dropping the 6, dividing 20 by 2 after a correct subtraction and then adding something else, or copying the constant. The creator agent can propose “they forgot to subtract 6 from both sides.” The QA agent can confirm that x = 10 fails the original equation, because 2(10) + 6 = 26. It cannot confirm the story. That attempt is marked uncertain and waits for an instructor, who may ask the learner for the middle line or may assign the blank-page walkthrough instead of a personalized video.

Filming the guessed story at the speed Golpo can draw is the failure this spoke exists to prevent. The learner who actually subtracted correctly and then mis-copied the result will be told they do not understand balancing. That is a new error, introduced by the course, and it is harder to undo than a delayed video. The instructor queue should show the missing middle line as the reason, not a generic “QA failed” badge. Staff can then request the work, assign the general walkthrough, or write a diagnosis they are willing to sign.

When the middle line is present, the video’s sequence is fixed. Show the original equation. Show the learner’s line unchanged. Substitute and land on the broken value, 26 or 19 in the pilots. Then show the legal line and its successful substitution, 20 or 16. End. A closing pep talk, a streak count, or a claim about how many learners make this mistake is not in the source. The QA agent rejects those sentences because they have no recomputation and no citation. The drawing can be warm without becoming a statistic the course invented.

Store the check values in the attempt row exactly, so a later appeal does not depend on replaying the video. For the first constructed submission the row holds equation 2x + 6 = 20, learner line 2x = 20, learner value 10, broken check 26, corrected value 7, successful check 20. For the second it holds 2(x + 3) = 16, learner line 2x + 3 = 16, learner value 6.5, broken check 19, corrected value 5, successful check 16. An instructor reviewing a complaint can recompute from the row without trusting the pictures. If the row and the video disagree, the video loses. The attempt returns to blocked, the script is regenerated only from the row, and the old file ID stays in the history with a failed watch-back. Students are not asked to decide which of the course’s artifacts is the real correction.

Automate it: review gates and publishing with the Golpo API

For wrong-step explanations, the whole path from source to published lesson can run as one pipeline on the course platform. An agent in Codex with the Golpo Codex Skill, in Claude Code with the Golpo Claude Skill, or in Cursor, VS Code with GitHub Copilot, Claude Code, Claude Desktop, or Visual Studio through the Golpo MCP server can call the Golpo API, wait for the render, and hand the file to the platform's review steps. Production stops being the limit on how many checked lessons a course can offer.

1. Attach the reference first. Store the answer key and the learner's submitted work with the lesson before any script is drafted.
2. Review the script against the reference before rendering. If a solution or source exists, the platform's QA agent checks the draft against it: it re-solves, re-adds, or re-reads, then compares. A mismatch or an uncertain result stops the job before Golpo renders anything.
3. Generate with Golpo. The agent sends the approved script in Script Mode, with the course's locked style, voice, Video Instructions, and Voice Instructions.
4. Transcribe what was actually said. Run speech-to-text on the finished video's audio. Learners hear the transcript, not the draft.
5. Run two independent transcript reviews. Make two separate LLM calls, separate from the creator agent and the QA agent. Each gets only the transcript and the reference, with no access to the draft or to the other reviewer's verdict. Each checks every spoken number, term, and claim, then returns pass or fail and quotes the line it objects to. The lesson moves on only when both pass. A failure or a disagreement goes to an instructor.
6. Check the frames. Pull a frame every few seconds and confirm every number and label on screen matches the approved script.
7. Publish. The pipeline posts the video to the course platform or LMS through its API as a draft, then releases it under the course's own approval rule.

FAQ

Can these lessons be generated and published automatically?

Yes, on the course platform's side. Using the Golpo MCP server or the Golpo Claude Skill, a pipeline can check the script against the answer key and the learner's submitted work, generate the video, run two independent transcript reviews, and post the lesson to the platform as a draft. Anything that fails a check goes to an instructor.

Why not just show the correct solution?

The correct solution is the exercise walkthrough. This lesson exists because a specific line was submitted. The learner’s line, the value that breaks it, and the repaired line are all required.

What is wrong with 2x = 20 from 2x + 6 = 20?

Subtracting 6 from both sides leaves 2x = 14 and x = 7. Then 2(7) + 6 = 20. The learner’s x = 10 gives 2(10) + 6 = 26. The QA agent should compute both.

What is wrong with 2x + 3 = 16 from 2(x + 3) = 16?

The 2 has to multiply the 3 as well. The expansion is 2x + 6 = 16, so x = 5, and 2(5 + 3) = 16. The learner’s 6.5 gives 2(6.5 + 3) = 19.

Who decides the diagnosis is fair?

The platform’s QA agent checks the substitutions. If the middle step was never stored, the attempt should be marked uncertain and sent to an instructor. Golpo does not infer what the learner meant.

Can the same video be reused for every student who misses the item?

Only when they missed it in the same way. A student who distributed correctly and then added wrong needs a different script. Same item ID, different error code, different lesson.

Where does the API job fit?

On the Explain This spoke. This page is the teaching pattern inside the script. That page is the generate call, the stored job ID, the poll, and the instructor hold.

What should the watch-back compare?

The drawn learner line against the stored line, the corrected line against the recomputation, and the two check values, 26 and 20 in the first lesson, 19 and 16 in the second. A swapped label fails the release.

Related guides

• Checked lesson videos — the release rule around any diagnosis.
• Explain This — Algebra Practice Studio’s path from approval to job ID.
• Exercise walkthroughs — start from a blank page instead of a wrong line.
• Exam-question explainers — one pasted question, one video.
• Lesson plus practice — a pause for a try before any error exists.

Quote the line the learner wrote, substitute both values, and render only the script in which those substitutions agree.