Mini Calculator.

Capstone: a tiny budget calculator on the page. Read income and expense from inputs, compute remaining, show it, and mark the panel with class ok or bad.

Combines querySelector, value, Number, textContent, classList, and click.

Mini plan:

1) listen for #calc click 2) remaining = Number(income.value) - Number(expense.value) 3) #remaining textContent = String(remaining) 4) if remaining >= 0 → classList add ok, remove bad; else the opposite

Common mistake: swapping income/expense; or leaving the old class on.