reasons

I'm an older C# and wordpress dev looking for work. It seems interviewers want me to know my stuff backwards and forwards now. I'm fine with that, but I don't know what to aim for. I've always just built stuff; never saw a need to memorize C# in its entirety or study big O notation to CSS better. Has the nature of the actual work changed drastically or is this merely a matter of interviews evolving to a crazy competitive level? For context it's been seven years since I've gone through this process.

Alright HN, tell me what to build. Top voted idea wins. Keep in mind I am one guy and the budget is reasonable hosting costs and 3 months to build. Don't bore me!! Will post a follow up.