Second Guess: flashcards that notice when you're guessing

This is a submission for the Presage SmartSpectra SDK Challenge.

Second Guess helps students find the answers they only guessed right, without trusting their own over-confident self-ratings.

What I Built

The problem. Flashcard apps like Anki and Quizlet decide when you'll see a card again from your own rating — and people overrate lucky guesses. A guess gets scheduled like real knowledge, pushed a week away, and forgotten. You find out in the exam.

What it does. Second Guess watches the few seconds between seeing a question and revealing the answer — the recall window — using the SmartSpectra SDK. If you got it right but hesitated (a long pause, looking away, a held breath), it says "Right — but you hesitated: long pause, looked away" and brings that card back tomorrow instead of next week. Every signal is compared with your own 60-second warm-up, and you can always disagree with one key.

Demo

Live SDK signals on my laptop: breathing trace, blinks, expressions and the 478-point face mesh — numbers only, no video kept.

Camera check: plain hints and a face-points "mirror" instead of a video preview.

Summary, Check mode result and signal replay.

Code

softalpha0 / second-guess

Second Guess

Second Guess helps students find the answers they only guessed right, without trusting their own over-confident self-ratings.

A desktop flashcard app that watches for hesitation while you recall an answer — using your webcam and the Presage SmartSpectra SDK. When a right answer was really a guess, it says "Right — but you hesitated" and brings that card back tomorrow instead of next week.

🎬 Demo video (1:27)	https://youtu.be/Bw7pHNqaJRY
📝 DEV post	https://dev.to/softalpha_0/second-guess-flashcards-that-notice-when-youre-guessing-4d9n
🧾 Evidence	docs/evidence — SDK field report from a real run, honest accuracy results, test results

Built for the Presage SmartSpectra SDK Challenge on DEV · categories: Best Thoughtful Real-World Use, Most Creative or Delightful Use.

⚠️ Second Guess measures study hesitation — not stress, emotion or health. It is not a medical device.

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The problem

Spaced-repetition apps (Anki, Quizlet, Brainscape) decide when you see a card again from your own rating of how…

View on GitHub

Run it from source in four commands (see the README). Evidence (SDK field report from a real run, test results, honest accuracy numbers): docs/evidence.

How It Responds to Human Signals

The SDK runs in Electron's main process on the native camera and sends ~20 messages per second. Before writing any feature, I logged every field it sent on my Windows laptop (field report). That spike decided the design: a 478-point face mesh including irises (great for "looking away"), blinks, the chest-breathing trace and 8 expression scores at ~25 readings/s — and pulse only twice in 77 seconds.

Signal	SDK source	What counts as hesitation	Weight
Long pause	app timing	Much slower than your pace on this deck (long questions get a reading allowance)	55
Looking away	face.landmarks → head + eye direction	Away from your usual direction > ~1 s	30
Breath hold	breathing.upperTrace	Nearly flat for 2–4 s	20
Blinking	face.blinking	A burst, or none when some were expected	15
Expression	face.expression	Moving away from your resting face	15
Pulse	cardio.pulseRate	Not used per card — too slow for a 3-second recall	0

The weighted sum is a 0–100 score (threshold 50, adjustable); the two biggest contributors become the plain-language reasons. When the signal is poor — face lost, too dark, camera stopped — the card is marked "no reading" and scheduled normally. SDK validation codes become plain hints on the camera check ("More light on your face, please").

Does it work? Honest results

Check mode asks "Was that a guess?" after each right answer and hides its own verdict. In a first test of 16 right answers of my own study, Second Guess caught all 5 of my guesses — but it also flagged 8 of the 11 answers I actually knew, so it agreed with me about half the time. That's cautious on purpose (a false alarm costs one extra review; a missed guess costs you in the exam), but it isn't good enough yet. The data already told me what to fix: see Challenges.

Challenges

• The warm-up was too easy. "2 + 2" takes a second; real cards take longer even when you know them, so every answer looked like a long pause. Recall time is now compared with your own pace on the real deck.
• Looking away pointed the wrong way for me — I glance at the keyboard when I'm sure. Check mode caught it; it's the next signal to re-tune.
• Pulse was too sparse per card, so it got weight 0 instead of pretending.
• The SDK needs the internet while running. A network drop stops the camera, so the app explains exactly why and offers "Turn camera back on".

How I built it

• Electron + TypeScript + Vite, @smartspectra/node-sdk 3.5 in the main process (the API key never reaches the window).
• All scoring, scheduling, baseline and import logic is pure TypeScript in src/core with 104 Vitest tests.
• Local JSON storage; the API key is encrypted with Windows DPAPI via Electron safeStorage.
• Hand-written SVG for the progress chart and signal replay; electron-builder for the Windows installer.

What's next

• Re-tune with more Check-mode data and learn each user's weights from their own Y/N answers.
• A longer, varied warm-up so the baseline matches real cards from the first card.
• Anki export so "hesitated" verdicts can feed existing decks.

Prize Categories

• Best Thoughtful Real-World Use — it fixes a real flaw in spaced repetition, with consent first, no recording, "no reading" instead of guessing, and an honest measurement of its own accuracy.
• Most Creative or Delightful Use — physiological signals used not for health, but to catch a lucky guess.

Consent and Data Handling

• The camera starts only after a consent screen that explains what's measured, kept and sent. A Camera on indicator and Stop camera button are always visible.
• No video, frames or images are stored or sent by Second Guess. The app never subscribes to the SDK's video output. Per card it keeps only the hesitation score, the reason labels and the recall time, in local JSON files.
• The SmartSpectra SDK processes the camera on the computer. It connects to Presage's servers to verify the API key and download its models — those requests are linked to the key, so I don't call it anonymous. SDK telemetry is off (enableTelemetry: false); per Presage's Telemetry & Privacy page, telemetry never includes frames or measured values anyway.
• Settings → Delete all data removes history, schedule, imported decks, settings, the saved key and logs.
• It measures study hesitation — never stress, emotion or health. No AI services are used by the app.
• No camera or key? It works as plain flashcards, with a clear notice.

Agent Session

I built Second Guess solo with Claude Code, from a written PRD and a CLAUDE.md of rules (plan first, one feature at a time, pure tested core, no video stored, no health words). The riskiest part went first: an SDK spike on my own laptop that logged every field the SDK sends.

Two real prompts from the session:

"read CLAUDE.md and this file. Explain your plan in plain language and wait for approval. Build in the order of §7. The riskiest part (M1: what the SDK really gives us) comes first. Test after each feature, commit, then move on."

"build everything that needs to built today"

Claude Code wrote the code and tests; I tested every feature on my own laptop and webcam, reported bugs from real use (a camera that stopped, a misleading banner, false alarms), and the fixes came from that real data.