Learning Assembly

The first of the fabled Five Pillars, The Professor is the master of languages and ways to communicate with and interpret the Weave. To pass his trial and prove yourself worthy, you must demonstrate your mastery of the old tongue. Fail, and who knows what will happen…

Inline assembly is written in the Yul language. In this quest, learn about the basics of the language and the incorporation of inline assembly into Solidity contracts.

Inline Yul Assembly

Simple Arithmetic

Comparisons

Assembly If statement

Assembly Switch statement

Assembly For statement

Assembly SafeMath

You lose track of time, answering the Professor’s many questions and riddles as fast as you can. You thought you knew the old tongue pretty well, but he makes you feel like a beginner. 

Then, just as you begin to feel you’re completely out of your depth, he stops and lets a slight grin touch his lips.

Well done, Guardian. You can color me impressed! Not many people, even in the Academy, have such a grasp of the ancient languages.

You smile. I get the impression he isn’t impressed by many people. It appears your years of study have paid off. 

But if this was only the first test, you dread to think what’s coming next…

You have traveled far, and now stand facing the hidden door to the Pillars’ sanctum. A place of legends, known only by those deemed worthy.

Before you can knock, the door opens, and you find yourself facing an eccentric old man. He wears a simple robe, and has a deeply knowing look in his eyes. 

Guardian, you have answered our call. I am the Professor, first of the Pillars. I only hope you will prove to be enough…

Ushering you through the door, the Professor fills you in on what you have let yourself in for. You must pass four perilous trials, one set by each of the living Pillars. Pass all four, and you will be accepted into their number. Fail, and… well, you would not be the first to pass through these doors never to return. Only the most brilliant can join the Pillars, and anyone who fails to prove themselves can’t be allowed to speak of what they saw down here.

Let the trials begin. You will have to first face the Professor’s test to proceed…

In this quest, we have learnt how to use basic inline assembly syntax to:

These seem like a lot of opcodes. However, just like programming in most languages, there is no need to memorize syntax nor function names. All we need to know is that they are available and which documentation we can refer to.

Inline assembly creates more complex and less readable code than regular Solidity. Furthermore, without type checking, variables can silently underflow or overflow, resulting in sneaky vulnerabilities in our smart contracts.

So why do we use it? Inline assembly gives us more control over the final compiled bytecode. As we will see further into the campaign, this allows interesting actions and gas optimizations.

Yul Basics

Here is an odd puzzle for any self-proclaimed EVM master. See if you can build an "Ouroboros", and prove your mastery over low-level bytecode sorcery.

Finding Ouroboros

Starknet contracts support state variables, but how they live in contract storage is generally abstracted away from the typical developer. In this quest, we will take a peek under the hood and see how state variables are stored exactly.

Starknet Storage Layout

Do you know how low-level calls work in Starknet? Or how calldata is encoded? This knowledge could be useful for on-chain sleuthing and some other advanced use cases. 

Learn about the inner workings of calls and calldata in this fun interface spoofing exercise!

Calldata Spoofing

Starknet contract addresses, like in many other blockchains, can be precomputed too. This allows for the creation of vanity addresses.

In this quest, see if you can deploy your smart contract under a specified address pattern...

Vanity Addresses

Can we build an EVM inside of an EVM? That seems like a strange question, but the answer is yes we can! In this quest, we will build a self-hosted EVM (sEVM), squeezed into a single smart contract. By rebuilding the EVM, develop a deeper appreciation of the machine's inner workings and EVM bytecode.