Adventure Land uses Stripe to handle payments, the leader in payments processing. Your credit card information never touches Adventure Land's servers.
SHELLS are Adventure Land's rare, purchasable currency. Unlike many other games, you can find SHELLS in-game too. They drop from gems and monsters. They are rare.
This creates equal opportunities for all players. You can only purchase non-essentials with SHELLS, like cosmetics and extra bank storage, to ensure the game is not pay-to-win.
You can support Adventure Land's development by buying SHELLS and hopefully enjoy the game more, faster, to your hearts desire!