September 13, 2021
Inside Clarity Universe Vol 1:
100+ Developers Are Learning To Write Smart Contracts For Bitcoin
by Caitlin Eckvahl on September 13, 2021

On September 1, we welcomed our very first Clarity Universe cohort, ushering in more than 100 new builders. Clarity Universe was created to provide developers everything they need to be successful with smart contracts for Bitcoin in one place. The program is made of three key parts: Clarity Talent, Clarity Starters, and Clarity Camp.

Clarity Talent helps match Clarity needs within our developer talent pool, Clarity Starters offers ready-made smart contracts for use, while Clarity Camp is the 6-week immersive learning experience that guides developers through everything they’ll need to create Bitcoin-supported applications and powerful smart contracts.

Every so often, we’ll be taking a peek into this inaugural Clarity Camp to deliver highlights from the program and tell the noble stories of our Bitcoin builders. Students will graduate with the tools necessary to create web applications fit for the growing Bitcoin economy including innovative DeFi, NFT, and Web 3.0 use cases.
Class is in session
This cohort’s Clarity Camp professors feature Marvin Janssen, the Stacks Foundations’ technical lead and resident Clarity expert, and Tina Lee, Founder of the Z Institute who has led the most popular online blockchain course in Taiwan. Together, the duo attracted more than 140 promising students to the opening of Clarity Camp where class kicked off with a crypto 101 ice breaker. Covering everything from“seed phrase” to “strong hands”, students demystified crypto jargon and tested their knowledge of key blockchain concepts.
Image provided by Tina Lee (Lee Ting Ting), Founder of the Z Institute.
Lesson #1: Blockchain Basics
After digging into some crypto basics, students regrouped in session #2 with Tina to learn what a blockchain is, how it works, and why they were created in order to make educated design choices when creating their first decentralized application.

Tina took students through the history of blockchain and explained how the concept of blockchains were first introduced to address pain points within the banking process. While blockchain is largely touted as a major innovation to bring increased transparency to the financial world, students also learned that blockchain is quickly being applied to address broader issues within other industries such as food, healthcare, and art.

Students ultimately learned that blockchain is still in its infancy, but this is an opportunity not a drawback. Clarity Campers left feeling empowered and ready to apply their working knowledge to design and develop new use cases and applications that borrow from both blockchain and Bitcoin-powered smart contracts.
Putting Gears in Motion
In session #3, Marvin helped students apply their newfound blockchain knowledge by creating their very first smart contract using Clarity. Before getting into the interactive part of the session, Marvin posed the question,“Would you sign a contract in a language you cannot read?” When you go to the bank for a mortgage or sign a contract for a new job, you would find yourself hard-pressed to sign any kind of legally binding document that you could not make sense of. The same should apply to smart contracts.

Take a look at some of the properties that make that possible as well as some of the other properties that make Clarity so unique compared to other smart contract languages.
Graphic provided by the Stacks Community. Statistics referenced here.
  • Contracts are readable. Clarity is interpreted which makes its so the smart contracts that hit the chain are readable.Anyone can pluck out the contract, inspect the source code, and be able to know what it means. By contrast, only 1% of all smart contracts in Solidity have source code available, requiring users to blindly trust developers.
  • Extra protection. Stacks transactions are secured by post conditions, which are double checks that are executed at the end to make sure nothing is amiss. Post conditions are important because if something doesn’t add up, the contract will revert back to its original state and provide details on why the transaction was not successful.
  • You know the cost upfront. Clarity’s decidability makes it so you know the maximum run-time cost with certainty. This is not possible for languages that are not decidable, the best you can do is an educated guess(think of gas estimates for ETH peeps).

Students put this into practice and created their very first Clarity smart contract on Clarinet (shoutout to Hiro for making this possible), a development tool where you can develop, test, and deploy your contract as well as run contract calls against it to ensure smooth testing.As part of the Clarity Camp program, students are also provided with complimentary access to Codeacademy where they can access Clarity Camp material and exercises, as well as the entirety of the Codeacademy library.
Boom Wallet Show and Tell
For session #4, students concluded their first week of Clarity Camp with a proper Show and Tell from Dan Trevino, who recently used Clarity to build Boom Wallet, a new application that allows users to participate in"delegated stacking” and lock STX up in the form of a limited-edition NFT.

Dan shared a bit about his recent experience using Clarity and provided some hope for those who are brand new to the language,“When you look at some code you can immediately tell what's happening.”

Here are his top tips for students and beginners learning Clarity:
  • Hit the library. The development libraries contained in stacks.js are a super helpful resource to make building applications easier. There’s a number of functional resources that developers can tap into that can help beginners start working with the Stacks blockchain.
  • Catch bugs fast! Clarinet is awesome for showing you errors, it highlights things that are incorrect right off the bat.
  • Best way to version contracts? Dan shared that this is something to consider ahead of time and that he found it helpful to break contracts into smaller, more discreet parts since there isn’t a good way to just upgrade. Best course of action is to modularize support for contracts within the code.

First Edition Boom NFT
Credit: Boom Wallet at
What’s Next
Looking ahead at the Clarity Camp syllabus, students will soon be creating a contract that manages tokens over time and hear from speakers who will discuss bringing NFTs to Bitcoin as well as a deep dive into Proof-of-Transfer (PoX). Students will also take a virtual field trip to Miami to learn more about Freehold and what it’s doing with CityCoins, and learn more about how they can put their newfound skills to work in an upcoming hackathon.

By the end of the 6 weeks, students will have both the knowledge and proficiency to enter the growing Clarity job market. Stay tuned for more stories following our Bitcoin builders!

Caitlin is the Communications Lead at the Stacks Foundation where she provides PR and communications support to Stacks builders. Previously, she worked as a communications consultant at Wachsman where she worked with prominent crypto and blockchain companies including Stacks,, Rarible, Qredo, Value Technology Foundation, Status.IM, Binance Charity, and others.