FOIL. FREE
Why Product Science GitHub Get Foil · $0
The problem was never you
You're not bad at it.
You were taught it wrong.
Watch Crux teach itself. Pick a subject.
Physics · Quadratics
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VERTEX ON THE CURVE
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NOT A TRIAL · NO CREDIT CARD · NO API KEY · NO ACCOUNT
0%
More students fail under lecturing than active learning — PNAS 2014
2/3
Gone by tomorrow without retrieval — Ebbinghaus, 2015
0+
Learning-science techniques in every session
$0
Cost. Forever. No trial, no card on file
The part nobody tells you
Why the lecture didn't stick.
01

Attention flickers every 3–4 minutes. Nobody's brain holds a lecture-length buffer.

Bunce et al., 2010
02

Watching a solved problem feels like understanding it. That feeling is a well-documented illusion.

Bjork & Bjork — fluency illusion
03

Two-thirds of what you heard is gone by tomorrow — unless you pull it back out first.

Ebbinghaus, replicated 2015
04

One teacher, thirty paces. And the more an expert knows, the more steps they skip without noticing.

Curse of knowledge
05

33.8% fail under lecture. 21.8% fail under active learning. Same students, same exams.

Freeman et al., PNAS 2014
06

So you decided you were the dumb one. You weren't — you were taught wrong.

Learned helplessness
x = ½at² · v = at CLICK TO RELAUNCH
So we built the exact opposite
Every one of those, engineered against.
Attention flickers, unnoticed
→
Foil watches for the exact moment
Fluency fools you
→
Refuses to be fluent for you
Gone within 24 hours
→
FSRS schedules against the curve
One teacher, thirty paces
→
One tutor, one brain: yours
Skipped steps you never saw
→
Can't skip what it isn't explaining
"I'm just not smart enough"
→
Tuned so you keep winning
a = −(k/m)x − cv DRAG THE MASS
Everything, built in
Not a chatbot with a system prompt.
Socratic sessions
Never the answer. Always the next question.
Live whiteboard
Draws stroke by stroke on an infinite canvas.
Realistic voice
Full spoken back-and-forth, natural neural voice.
Crux, the agent
Builds courses from a syllabus, reads your homework.
Mastery tracking
Live probability-of-mastery, not a letter grade.
FSRS flashcards
Auto-generated, scheduled by real spaced repetition.
Reels
A retrieval feed built against TikTok, on purpose.
SAT / ACT prep
Timed modules, pattern drills, error analytics.
Not vibes — research
Every technique has a real study behind it.
2σ
Bloom's 1984 tutoring result — never reproduced at that size. The target we're chasing, not a promise kept.
Self-Determination Theory
Competence, autonomy, relatedness — in every reply.
The Socratic Method
Retrieving it yourself builds a trace being told doesn't.
The Protégé Effect
Teach-back hands you the chalk.
Retrieval Practice
Graded recall, never a passive re-read.
Spaced Repetition (FSRS)
Review lands right before you'd forget.
Desirable Difficulties
Slower now, far more durable later.
Bayesian Knowledge Tracing
A live probability you've actually mastered it.
Attribution Repair
Struggle gets named as progress, not identity.
Let's just say it out loud
But you're probably wondering…
"Isn't this just ChatGPT with extra steps?"
ChatGPT answers fast. Foil refuses — it tracks mastery, draws on a whiteboard, and watches for silence, because answering was never the hard part.
"Why is it free? What's the catch?"
No catch. Built by a high-schooler who needed it for his own classes. No card, no trial, no locked tier.
"Won't an AI tutor just let me cheat?"
Paste homework in and you get asked what you've tried, not a solution. If you want the worksheet filled in, this is the wrong tool.
"I don't have time to learn another app."
Twenty seconds. Click a topic, it starts talking and drawing. That's the entire onboarding.
"I've genuinely always been bad at this."
That belief is almost always a conclusion about the delivery method, not you. Twenty minutes will test it.
How it's actually built
One codebase, every surface.
One React app ships as a native desktop build and a full browser build — local SQLite, or the same engine in WebAssembly. Gemini powers tutoring, vision and voice; a pooled-key proxy means no one needs their own API key.
Early access
Built with real students, right now.
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$0 — NOT A TRIAL, NOT FREEMIUM, NO CARD, EVER
Find out how your brain
was supposed to learn.
WINDOWS
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Unsigned beta — if Windows warns, click More info → Run anyway.
macOS
FREE
↓ Apple Silicon ↓ Intel
Won't open? Tap for the fix
Gatekeeper is strict about unsigned downloads. Try System Settings → Privacy & Security → Open Anyway, or run xattr -cr /Applications/Foil.app in Terminal.
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FOIL. — companion: Crux
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