If you bought a Croodle (they're now sold out ), you may have seen that the transaction cost was low as $20 when gas prices were around 80-70 gwei, which is the most common range.

So how does it works? I've used a custom ERC721 contract that uses a super efficient minting mechanism created by @squeebo_nft as well as a lot of modified variables and functions, maintaining all the original features.

And how about the Enumerable set of functions? The @OpenZeppelin implementation has a lot of unnecessary variable assignments, so I cut all of that and created "free" functions that does not require storing data simply by reading dynamic data from the contract. Inspired by @0xInuarashi.

If you are interested in digging deeper into these contracts and all the source files, you can checkout the Croodles official code and the Sol-Temple repo, where I store all my contracts.