---
# System prepended metadata

title: '::: The Z Institute Class Note :::'

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# ::: The Z Institute Class Note :::

- **Participants:**
    - Lemonde (TW)
    - Walter (TW)
    - Ethan (TW)



## Notes 

Ethereum Virtual Machine (EVM)

ERC1155 可以多很多copy

ERC721 一次只能一個

Mainnet-fork : https://hardhat.org/hardhat-network/guides/mainnet-forking.html

Layer2:
* Notable Layer 2 networks
Since its launch, many Layer 2 solutions have successfully gained attention in the crypto world. Here are the notable layer 2 solutions that resolved several critical problems.

* Polygon - It is an emerging platform meant to develop and connect Ethereum-based blockchain networks. It features all the tools and components used by developers to create optimized Ethereum instances. Also, the platform provides an improvement in flexibility for developers and the security of Ethereum. Polygon is steadily becoming the preferred Ethereum Layer 2 solutions provider and is seeing incredible market growth.
* 
* Arbitrum - It is another notable entry among the popular Layer 2 solutions providers for several reasons. Arbitum development has features meant for close interoperability with Etherum. These features make it easy for Solidity developers to cross-compile their smart contracts. The three components of Arbitum include a compiler, the EthBridge and validators.  Arbitum does not feature a native token and indicates that it is not interested in launching one.
* 
* Another highlight to Arbitum is that it supports sidechain aggregation of transactions or rollup technology.
* 
* Optimism - This is another example of famous Ethereum scaling solutions that provide improvements to transaction affordability. Also, it can ensure prolific improvements in transaction speed for Ethereum users. Developers here can create Solidity smart contracts with some limitations.
* 
* One of the striking highlights of Optimism is the direct collaboration with Synthetix. The platform announced it would provide staking options to users with SNX tokens.
* 
* Immutable-X - Immutable- X is the first Layer 2 scaling solution for NFTs on Ethereum. It provides instant trade confirmation, zero gas fees, impeccable scalability and provides this without compromising on user custody. The protocol operation on top of StarkWare’s proves the technology and allows users to retain Ethereum’s network and services.
* 
* X-Dai - is a sidechain based on Etherum and supports users in processing transactions at economical costs and faster speeds. The platform uses a PoS consensus mechanic to help users place native xDAI tokens as stakes on the networks. The most enticing part about xDAI is that it is a stablecoin.
* 
* The growth of the xDAI system comes about thanks to its integrations and partnerships with other platforms and projects.

Random number: https://chain.link/chainlink-vrf

https://solidity-by-example.org/hacks/block-timestamp-manipulation/



## Resources
https://docs.openzeppelin.com/contracts/4.x/
https://hardhat.org/hardhat-network/guides/mainnet-forking.html
https://chain.link/chainlink-vrf
https://solidity-by-example.org/hacks/block-timestamp-manipulation/
https://medium.com/@daniel.mars622/%E4%BB%A5%E5%A4%AA%E5%9D%8A%E5%8D%80%E5%A1%8A%E9%8F%88%E6%99%BA%E8%83%BD%E5%90%88%E7%B4%84%E5%9F%BA%E7%A4%8E%E4%BB%8B%E7%B4%B9-b7317347a612
