- What it is
- A shared trip planner where friends add plans to a day-by-day itinerary, vote when two plans clash, and build a packing list together.
- Why I made it
- I wanted a group trip to have one shared plan instead of living in a giant group chat.
- What I did
- I built it in August 2025 with Flask and plain JavaScript, with live updates and JSON files that lock, so two people saving at once can't wipe each other out.
- How it turned out
- Everyone sees changes right away without refreshing. If more than a few friends used it, a real database would be the next step.
The details
Planning outside the group chat
Anyone on the trip can add an event with a time, place, notes or a link, and everyone else sees it without refreshing. I kept the front end to plain HTML, CSS and JavaScript so it stayed small and simple.
Voting on conflicts
If two plans land at the same time, they turn into options and everyone votes them up or down. You can only delete your own plans, unless you're an admin, or everyone else has voted it down.
Packing together
There's also a shared packing list, split into items, snacks and other stuff. You can heart the good ideas, and it remembers who hearted what.
Under the hood
Live updates use Server-Sent Events: when anything changes, the server tells every open browser to refresh that part of the page. Everything is saved in JSON files with a lock, so two people saving at the same time can't wipe each other out. A real database would be the next step if more than a few friends used it.
Admins can add people and reset passwords. 
Adding an event. Only the title is required.