Visual guide4 min
What problem does a blockchain solve?
A shared record is easy to copy. Agreeing which changes count is the harder part.
Read the guideThe learning library
Make sense of the mechanisms.
Follow a question, experiment with an idea, or take the guided path. There’s more than one way to understand.
Start here
Follow a Bitcoin payment
An everyday action connects wallets, outputs, fees, and confirmation. Read the path in order, at your own pace.
01Your wallet, your keys, and your bitcoin: what lives where?
02What actually happens when you send bitcoin?
03UTXOs and change: why one payment can create two outputs
04Bitcoin transaction fees and virtual size
05Pending, confirmed, and reorganized: a payment’s changing status
06How a Lightning channel works
18 published articles
Interactive lesson3 min
Hashing explained: change one character and inspect the result
Turn a message into a fingerprint, then see how a tiny edit changes the result.
Explore the lessonVisual guide4 min
Hashing versus encryption: why they solve different problems
One helps compare data. The other helps keep data confidential. Mixing them up breaks the design.
Read the guideVisual guide3 min
Private keys, public keys, and addresses
Three things often called “a wallet address” do very different jobs.
Read the guideVisual guide3 min
What does a digital signature prove?
A valid signature connects a message to a key. It leaves several other questions unanswered.
Read the guideVisual guide3 min
What nodes check, and why a blockchain needs consensus
Validity, willingness to relay, and choosing a history are three separate decisions.
Read the guideInteractive lesson4 min
What actually happens when you send bitcoin?
Follow one payment from your wallet to a block, and account for every sat along the way.
Explore the lessonVisual guide3 min
Your wallet, your keys, and your bitcoin: what lives where?
Separate the app on your phone from signing authority and the outputs recorded by the network.
Read the guideVisual guide3 min
UTXOs and change: why one payment can create two outputs
Work through coin selection without imagining a single account balance being edited.
Read the guideVisual guide3 min
Bitcoin transaction fees and virtual size
A bigger payment does not necessarily make a bigger transaction. Separate amount, size, rate, and total fee.
Read the guideVisual guide3 min
Pending, confirmed, and reorganized: a payment’s changing status
A status label is an observation about a transaction and a chain, not a promise about the future.
Read the guideVisual guide3 min
Read a Bitcoin transaction explorer without getting lost
Use a fictional transaction to separate recorded facts from an explorer’s interpretations.
Read the guideVisual guide3 min
How a Lightning channel works
A channel changes claims to allocated funds without recording every payment as a new on-chain transaction.
Read the guideInteractive lesson4 min
Why can a Lightning node send but not receive?
The same channel can have plenty of capacity and very little room for a payment in one direction.
Explore the lessonVisual guide3 min
On-chain and Lightning payments: what changes for the user?
Compare the payment journey, including setup, completion signals and failure cases.
Read the guideVisual guide3 min
What happens inside a crypto checkout?
An invoice, a payment observation, and an order are related records—not the same thing.
Read the guideVisual guide4 min
Why a webhook can arrive more than once
Design a repeated notification to produce one business effect, even when acknowledgments get lost.
Read the guideVisual guide4 min
Payment received versus order fulfilled: designing clear statuses
Keep financial observations separate from the decision to deliver a product.
Read the guide