This one's small, and it exists because a real problem needed solving: logging casual restaurant shift hours and knowing what they add up to, without a spreadsheet. I built it as a single-page app, no backend and no build step, just HTML, CSS, and JavaScript running entirely in the browser.
The main screen is a clock in/out form: pick a date, enter a time in and a time out, save. It immediately rolls that into hours for the day and a running total for the week, checked against a weekly target you can set. Everything is stored in the browser's own local storage, so there's no account, no server, and no data leaving the device.
Pay usually isn't flat across the week, weekends often pay more, so the app lets you set a separate hourly rate per day of the week and estimates earnings automatically instead of doing the maths by hand. The reports tab picks a date range and exports a signed-looking PDF timesheet, or the raw data as JSON, since everything only lives on that one device and is worth backing up.
It's a small project, but it's the kind that gets used every week rather than graded once: a real, recurring problem solved with the smallest tool that could actually do the job.