WIP version of the Double Decker deck for Balatro. Steamodded 0.9.8 required. May not work in Steamodded 1.0.0 yet.

DoubleDecker.lua

--- STEAMODDED HEADER
--- MOD_NAME: Double Decker
--- MOD_ID: DoubleDecker
--- MOD_AUTHOR: [Rokk]
--- MOD_DESCRIPTION: Adds a double-stacked deck to the game.

----------------------------------------------
------------MOD CODE -------------------------

-- Helper function to set a card's back sprite
local function set_card_back_sprite(card, desired_back)
	card.params.bypass_back = G.P_CENTERS[desired_back].pos
	card.children.back = Sprite(card.T.x, card.T.y, card.T.w, card.T.h, G.ASSET_ATLAS["centers"], card.params.bypass_back)
	card.children.back.states.hover = card.states.hover
	card.children.back.states.click = card.states.click
	card.children.back.states.drag = card.states.drag
	card.children.back.states.collide.can = false
	card.children.back:set_role({major = card, role_type = 'Glued', draw_major = card})
end

-- Add deck's booster effect variable and apply double card effect
local Back_apply_to_run_orig = Back.apply_to_run
function Back.apply_to_run(arg_56_0)
	local result = Back_apply_to_run_orig(arg_56_0)

	if arg_56_0.effect.config.extra_booster_selections then
		G.GAME.starting_params.extra_booster_selections = arg_56_0.effect.config.extra_booster_selections
	end
	
	if arg_56_0.effect.config.double_playing_cards then
		G.E_MANAGER:add_event(Event({
			func = function()
				-- Iterate over the initial deck, and deal an extra red-backed copy into the deck.
				local initial_deck_size = #G.playing_cards
				for i = initial_deck_size, 1, -1 do					
					-- Add copy and change its back to red card
					-- The game makes copying a card and adding it to the deck A LOT harder than it should be.
					-- Increment a global variable that governs deck size, copy the card, change its back sprite, and manually put it in the deck
					G.playing_card = initial_deck_size + i
					local copied_card = copy_card(G.playing_cards[i], nil, 1, G.playing_card)
					set_card_back_sprite(copied_card, 'b_red')
					G.deck:emplace(copied_card)
					G.playing_cards[G.playing_card] = copied_card
				end
				
				return true
			end
		}))
	end
	
	return result
end

-- Apply the deck's "extra booster pick" effect to opened booster packs
local card_open_orig = Card.open
function Card:open()

	-- Before calling the original function, add 1 to booster pack choices if the Double Deck is selected
	-- After the original function is called, set it back to the original value to prevent extra choices from accumulating infinitely
	
	-- Only apply to boosters and only apply if the player is using the Double Deck
	if self.ability.set ~= "Booster" or not G.GAME.starting_params.extra_booster_selections then
		return card_open_orig(self)
	end
	
	-- Add extra selection
	local old_choose = self.config.center.config.choose
	self.config.center.config.choose = self.config.center.config.choose or 1
	self.config.center.config.choose = math.min(self.config.center.config.choose + G.GAME.starting_params.extra_booster_selections, self.ability.extra)
	
	-- Call original function to open the pack
	local result = card_open_orig(self)
	
	-- Restore old selection amount
	self.config.center.config.choose = old_choose
	
	return result
end

-- Add deck definition to the game using Steamodded
-- Note: x and y refer to the location of the deck's back texture in the atlas, and this is 0-indexed which is unusual for Lua
local deck_double = SMODS.Deck:new("DoubleDeck", "double", {double_playing_cards = true, extra_booster_selections = 1, discards = 1}, {x = 0, y = 2},
	{
		name = "Double Decker",
		text = {
			"Start with {C:attention}104{} cards",
			"{C:attention}+1{} discard",
			"Choose an extra card",
			"in {C:attention}Booster Packs{}"
		},
    }
)
deck_double:register()

----------------------------------------------
------------MOD CODE END----------------------