Do your best to improve the code security of Solidity.

There're various of attack methods in solidity, that contracts include bug will be the heaven to hacker.
Beside, the Computer Organization course really help me, especially in storage.
Transform that between Hexadecimal, Decimal, Octal, Binary is very important for learning solidity.

// Ethernaut Useful Commands
player
'0x....'
contract.address
'0x....'

# Truffle
truffle compile
truffle test
truffle migrate  // open Ganache first
# or
truffle migrate --network rinkeby