It is definitely a trick question and code intentionally made to be vulnerable to have fun finding what’s wrong and why it is bad practice to do so :)

For those that want to have an actual go at it: when deploying it with hardhat for example, you can pass in Math.floor(Math.random()*1000) as the constructor argument and then see if you can derive the number on the first guess.

BTW @[email protected] was right. Anyone can view the contract deployment transaction and see the value of secretNumber that was passed as an argument to the constructor.