Not only has the game been built in Godot 4 to avoid Unity pricing hikes, but the developer is encouraging anyone interested to reverse engineer it and learn how it was done! Sequel to the most famous Deckbuilding game ever made. The developers consider the game source available and do not care if you pirate it.
What is Deckbuilding?
Deck-building games are card games where players create their own decks during gameplay, rather than before the game starts. Players typically start with a small deck and can buy new cards from a central market to enhance their decks as the game progresses.
Video on disassembling Slay the Spire 2
ptrlrd/spire-codex guides you through decompiling the game in 14 different languages and making an API.
GOG Wishlist, as the game is currently available through Steam for purchase.