The problem StarkPay solves

Any blockchain ecosystem needs decentralised payments for DAOs to be fully effective. DAOs are unlike corporations, somebody could contribute for a weekend, somebody could contribute for a year. Anonymous contributors are equally welcome as doxxed individuals.
Recurring payment service is an essential application of a decentralised economy.

Challenges we ran into

We wanted to use warp and transpile to cairo as we had no prior experience in Cairo but ran into a lot of errors. So we went ahead and implemented a bit simpler algorithm in Cairo. The syntax is a bit complicated, but we took reference from a lot of libraries, most notably https://github.com/cryptoleek-team/starknet-worldmap-billboard and https://github.com/jediswaplabs/JediSwap/tree/main/contracts