Hi HN,

While renovating my apartment, I was keeping track of all my tasks and meetings — things like “Buy paint” or “Meet the designer on Tuesday at 1PM” — in Apple Notes. And there were a lot of them. Anyone who’s done a renovation knows how endless those lists get.

Note-taking or to-do apps are great because it’s super easy to quickly jot down many small tasks. But they lack important things: notifications, day-based structure, sharing tasks or meetings with others so they appear in their calendars.

Traditional calendar apps do the opposite — they’re more interactive: you can set notifications, view by day, invite participants, etc. But they’re painful when you just want to add many simple tasks. Those “add event” forms feel huge and clunky.

So we thought — why not combine the ease of note-taking apps with the interactivity of calendars? That’s how the idea for Mainn.app was born — a simple yet powerful calendar reimagined from scratch, with features you won’t find anywhere else.

Key ideas:

- On any day, just place the cursor and add as many simple items as you want — “Fix the bike”, “Buy groceries” — no heavy forms, just type like in a to-do app.

- Want a timed event? Type “Gym 11” and pick 11:00 AM/PM from quick suggestions.

- Need a meeting like “Discuss design 11:00 Alex”? Choose a contact from your phonebook shown on suggestion panel while editing the event! Alex will automatically get an SMS invite, and once he installs the app, the event instantly appears in his calendar. Most people don’t know each other’s emails anymore, but everyone has phone numbers — so we built the calendar around that.

- You can contact participants directly via their preferred messengers (Signal, Telegram, WhatsApp, etc.).

- Add a location — and with one tap, launch maps or a taxi app to get there. Works for all participants.

- We also have classic to-do and shopping lists, and you can mark them as “Always show today” — so your daily agenda always includes your lists.

- Share lists with your spouse or friends from your contacts — they’ll get an SMS invite too, and once they install the app, you’ll have a shared list in real time.

- Google Calendar integration (currently read-only).

And the most fun — a Social Hub where you can:

- Check in at places,

- Create invites for sports, games, or activities with friends at a chosen location (via SMS invites),

- Make public invites — e.g. “Looking for a tennis partner nearby” — so people around you can join.

- Those who join get the event in their calendar and can chat or navigate there instantly.

- You can also favorite invites and revisit them later — all accessible right in the calendar.

Right now, it’s a lightweight but capable calendar for personal tasks + a social hub for planning real-life activities. Next, we want to add professional features — a booking module like Calendly, but designed for freelancers and small service providers (stylists, coaches, electricians, etc.) where they can set working hours, manage bookings, and even promote their services in the Social Hub.

We already have designs and part of it implemented.

We’re a small team (3 developers and a designer) working part-time, so there are still bugs and things to polish — please don’t judge too harshly :) We've got tons of ideas and if we had funding, we could go full-time and build a lot more monetizable services — we see huge potential here.

Would love to hear your feedback!

Thanks to everyone who read till the end!

— Andrew

Grounding LLMs with Symbolic Planning