The Project: Your Expense Tracker

The task

Build a tracker for your own expenses. Not a professional piece of software: something small, yours, that actually serves you — where you enter expenses, categorize them, and see where the money went over a month.

Why this exact task. First: it touches everything. It needs a plan, it needs files, it needs checks, it needs verifying that the totals add up. Second: it's yours. Not a throwaway fake exercise, but something you could actually use next week. Third: it checks itself. Either the numbers add up or they don't.

How to set it up, move by move

This isn't a theoretical recap: it's the sequence to actually follow.

• New, empty folder. The first ground rule is always the same: don't let it into places it doesn't need to be.

• Plan first. Switch to Plan mode and tell it what you want to get. Then actually read the plan: that's where you'll notice things you hadn't thought about — what happens with recurring expenses, how you want categories set up, what to do with an expense that falls between two of them.

• Declare your yardstick. How do you know it works? For example: the sum of the categories equals the total exactly; no expense is left without a category; if I add a test expense and then remove it, the totals go back to what they were before.

• One piece at a time. First, entering and saving an expense. Then categories. Then the monthly summary. Each piece has to work before you move on to the next one.

• Write down your rules. The moment you notice you're repeating a preference, put it in the instructions file instead of saying it again.

What not to do

• Don't ask for everything in one shot. You'll get something huge that doesn't work and that you won't know where to start taking apart.

• Don't accept without looking. If you catch yourself clicking "yes" nonstop, you've stopped directing — and this is the job where that matters most.

• Don't aim for the perfect program. The goal is something that works and is yours, not a product.

How you know you're done

When you can do these three things without touching anything by hand: enter an expense, find it under its category, see the month's total and have it check out.

If you get there, you've done something that three months ago you'd have considered out of your reach — and you did it without writing code: by directing whoever wrote it.

What's next

Once you've got it in hand, there's one lesson left: what you're taking home from all this, and where to go from here.

Did you get it?

Two minutes, no grade. Trying to answer — even getting it wrong — cements the concepts far more than rereading. Not in the mood? Skip it: the lesson still counts as complete.

1What's the right way to start the project?

Ask for everything at once and see what comes out New folder, plan first, and one piece at a time that actually works

2Why does our version only show up after your attempt?

To make you work hard for no reason Because looking at it first would make you copy instead of build, and comparing afterward teaches twice as much