Contra and Lovable just ran a challenge: build an appointment business where "can I book?" turns into "you're booked" with as little work for the owner as possible.
We liked the brief because it makes you design both sides at once: what the customer sees, and what the owner has to do afterwards.
Our entry was a horror escape room in New York. The site is a small pixel game that ends in a booking, and behind it the owner gets bookings, a waitlist for sold-out slots and a dashboard, all running on Lovable Cloud.