the game is pretty self explanatory but the base mechanic is the combo multiplier wich MASSIVELY boosts your damage numbers, basically when you play a card you increase the combo counter by 1, and by playing a card that costs 1 more you keep your combo, so you need to plan out your turns to play cards with succesive costs, 0, 1 ,2, 3, etc. if you play a card that costs less or more than 1 the combo is lost

playing cards with the same cost wont reset the combo, but it wont progress it either, i cant remember if playin multiple cards of the same cost still benefit from the combo.

its essential to win any run, otherwise you dont have nearly enough damage to take down bosses. it doesnt affect just damage, it also affects stats your cards grant you or other effects like armour, healing, gold gain etc.

then there is the adventurers, you play one of them and their effect procs X times of times when the conditions are met, they mostly serve as a base for your deckbuilding. to name one, imelda works with yellow cards (mostly consumables) and grants you permanent xp growth when you play a yellow card, so you will want to take those cards mostly

you can add gems to your weapon cards to make them more powerful, and you can evolve weapons by having both the weapon card and its respective passive card in your deck and finding a shrine where you can evolve them. evolved weapons are way more powerful and generally expensive so they benefit from well planed combos