What makes a daily web game worth coming back to?

I'm building a small browser-based daily puzzle project, and it made me think about something I'm curious to learn from other makers:

What actually makes users come back to a web product every day?

For daily puzzle or game products, I've been considering things like:

• streaks and progress tracking

• a consistent daily challenge

• leaderboards

• sharing results with friends

• difficulty progression

• unlocking new content

From your experience, which of these creates genuine long-term retention, and which ones tend to become noise?

I'm especially interested in hearing from people who have built products with recurring or daily usage.

What have you seen work?