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Your personal tutor for math and coding. Built by top learning experts from MIT and Harvard.

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Explore

Thousands of interactive lessons

Math

Foundational and advanced maths, visualised and interactive.

Data & AI

Build intuition for data, probability and machine learning.

Computer Science

Programming, algorithms and problem solving by doing.

Lesson 3 62% complete · nice work
Controls

Pills, everywhere

I’m a learner Secondary Disabled Math Science CS
I’m a learner Secondary ← hover state
Email address Focused field Focused ← focus ring rgba(0,0,0,.4) 0 0 0 2px

Every control is a full pill (radius 9999px). The primary is a green #29cc57 3D-pressable button; on hover its face border goes to #000000. Text links hover to #456dff. Body copy sits at a soft rgba(0,0,0,.4), never full black.

Typography

Serif headlines, sans everything else

Display h1 · CoFo Robert (Fraunces) · 50/55 · 500 · -0.5pxA world-class tutor
Section h2 · CoFo Robert (Fraunces) · 60/66 · 500 · -1.2pxMeet your tutor
Sub h3 · CoFo Brilliant (Inter) · 30/37.5 · 400 · -0.3pxAward-winning
Body p · CoFo Brilliant (Inter) · 20/30 · 400Your personal tutor for math and coding.
Button · CoFo Brilliant (Inter) · 16-20 · 500I’m a learner
Nav / wordmark · CoFo Brilliant (Inter) · 16 · 500Brilliant · Sign in
Palette

One green, many pale tints

Text
ink#000000
muted#656565
faint#999999
slate-text#364153
Accent & dark surfaces
green#29cc57
blue#3860be
link-hover#456dff
slate#27455c
Surfaces & borders
canvas#ffffff
warm-surface#f5f3f1
grey-surface#f8f8f8
tint-blue#f0f8fa
tint-green#e7eee2
tint-peach#ffede0
border#e4e4e4
Depth & motion

Soft, rounded, feedback-rich

9999px pill
20px card
17px card
50% circle
card 0 0 15px .1
button 0 4px 14px .05
lifted 0 0 25px .2

Motion carries the personality. Base transition all 0.3s ease; the interactive-lesson engine adds feedback keyframes — evalPulse, evalFlashHighlight, shakeX on wrong answers, fillProgress, popularCardShine, floatyNudge — with custom cubic-beziers, honouring one prefers-reduced-motion block. No animation library.