Capstone: Build & Share Your Own App

Capstone — build your own app

Twenty-plus tutorials behind you. Now the real test: an app nobody scripted for you. This is the lesson where you stop following and start building — the difference between someone who did a course and someone who can code.

The brief

Build one original Streamlit app that solves a problem *you* actually have. It must:

Do something useful — you'd genuinely use it monthly

Take input — at least 3 different widgets

Remember something — session state or a saved file

Look intentional — sidebar/columns layout, a metric or chart

Be deployed — live on the internet (the deployment lesson covers how)

Ideas if you're stuck

Study planner — subjects, hours logged, weekly progress chart

Water/fitness tracker — daily logging + streaks

Split-expense calculator — who owes whom after a trip

Flashcard revision app — your own questions, random order, score tracking

Recipe cost splitter — ingredients, quantities, per-person cost

The best capstone is boring. "Water tracker" beats "AI social network" every time, because boring gets *finished*.

The process (how real developers work)

Day 1 — Scope on paper. Write one sentence: "My app lets a user ____ so that ____." List your widgets. Sketch which panel holds what. If the sketch takes more than one page, cut features.

Day 2 — The ugly version. Build the *logic* with zero styling: inputs, state, and one output that proves the core idea works. This is the hardest day — everything after is decoration.

Day 3 — Layout and polish. Move controls to the sidebar, add columns, add a metric. Fix the three ugliest things. Stop.

Day 4 — Deploy and share. Push to GitHub, deploy free, send the link to one friend. Their reaction is your grade.

The rubric (grade yourself honestly)

Criteria	Question to ask
Works	Does it run without errors for a first-time user?
Useful	Would you open it again next week?
State	Does it remember data between interactions?
Layout	Can a stranger understand it in 10 seconds?
Deployed	Does it have a public URL?

When you're stuck (you will be)

Re-read the error — the last line names the problem

Reduce until it works — comment out half the app; does the half that remains run? Rebuild up from there

Find the closest tutorial — your capstone is almost always two of this course's apps combined

Timebox frustration — 30 minutes stuck, then change approach. Walking away for 10 minutes genuinely works (your brain debugs in the background)

After you ship

Add it to your portfolio, post it with #buildinpublic, and write down the three things you'd do differently — that list is the syllabus of your next project.

This is the end of the taught course — and the start of the actual skill. Everything from here, you build. 🚀