Act as a frontend developer with good UI taste, not a code generator.

Context:
I’m building a small habit tracking web app for personal use.
Users open it multiple times a day, so the UI must feel calm and effortless,
not flashy or marketing-oriented.

Tech stack:
- Next.js 14 (App Router)
- React + TypeScript
- Tailwind CSS
- Simple, custom components (no heavy UI library)

Vibe / Design intent:
- Neutral, muted color palette (gray, slate, soft accent)
- Generous spacing, breathable layout
- Minimal borders, avoid card overload
- Focus on readability and calmness
- Looks like a real product, not a demo or landing page
- No animations unless they add real clarity

UI scope:
Design the main “Today” screen that includes:
- A simple header with today’s date
- A list of habits with check/uncheck state
- Subtle visual feedback when a habit is completed
- A small progress indicator (daily completion, very minimal)

Constraints:
- Mobile-first, works well on small screens
- Use semantic HTML and accessible interactions
- Keep components easy to modify by hand later
- Avoid overengineering

Output:
1. Describe the layout and structure first (in words)
2. Then provide React + Tailwind code for the main screen
3. Keep the code clean, readable, and opinionated