So, you want to write a smart contract. Great! You’ve got dreams of decentralization, passive income, and maybe even a token named after your cat. But before you deploy and accidentally mint 2 billion extra tokens or lose everything in a reentrancy blackhole… sit down. Breathe. 1. Integer Overflow & UnderflowAh yes, the good old days (pre-Solidity 0.8.0) when subtracting 1 from 0 gave you 2⁵⁶-1 and nobody blinked. Rookie mistake:// Solidity <0.8.0 uint8 balance = 0; balance -= 1; // Surprise!...