A small library of visual proofs
Seeing why beats
memorizing that.
Short lessons where the picture does the arguing. You watch one true thing turn into the next until the result has nowhere left to hide.
Watch the reason arrive
Step through with the dots, the arrows on your keyboard, or by nudging the rail. Each step says one true thing and shows it.
Why a squared plus b squared equals c squared
One line through the whole shelf
Follow it in order or wander. Finishing a lesson fills its mark, and the line remembers where you were, even after you close the tab. 0 of 3 complete. The line keeps going as the shelf does.
How a lesson is made
Four moves, every time
A lesson is not a wall of text with a diagram stapled on. It is one picture, taken apart slowly enough that you never lose the thread.
- 01
Find the picture
Before a word is written we look for the single image that already contains the answer. If there isn't one, it isn't ready to be a lesson yet.
- 02
One claim per step
Each step says exactly one true thing and shows it. No step asks you to hold two new ideas at once. You can always point at what changed.
- 03
The one stroke that lands
Somewhere a single mark makes the whole thing obvious. We draw it in coral and we wait until the sentence has earned it.
- 04
Test it on a stranger
We sit someone who forgot their geometry in front of the lesson and watch. If their face changes at the right moment, it ships. If not, back to the picture.
What people write back
I have hated the Pythagoras formula since I was twelve. I watched the four triangles slide once and now I cannot un-see it. It is just true.
My daughter asked why triangles add up to 180 and for the first time I could actually show her instead of saying because they do.
I do not need this for anything. I just like the moment where the rectangle appears out of the circle. I have watched it more times than I will admit.
Free while the shelf is short
There are three lessons today and there will be more. While the library is small it is simply free, no account, no trial clock. If we ever charge for a bigger shelf we will say so plainly, here, first.
About
A library, not a course
Straightedge is not trying to teach you a syllabus. There is no unit test at the end and no badge to collect. Each lesson stands alone: a single result, shown until it is obvious, then left for you.
We build them slowly because the slow part is the whole point. A picture that has been argued with for three weeks is worth more than a hundred that were generated overnight.
Made by Ada Okonkwo and Rafael Lindqvist, two former classroom teachers. Written at a long table in Gothenburg.