Genre: Card Game

Expert blueprint for digital card games with data-driven design and juicy UI.

NEVER Do

• NEVER hardcode card effects in card scripts — Use Command pattern or effect_script Resource. Enables designers to create cards without code.
• NEVER use global_position for hand layout — Hand cards should use local positions relative to hand container. global_position breaks with camera movement.
• NEVER forget to shuffle discard into draw pile — When draw_pile is empty, reshuffle discard_pile. Otherwise game soft-locks.
• NEVER skip z_index management — Dragged cards must have highest z_index. Use move_to_front() or set z_index = 999.
• NEVER use instant card movements — Cards without tween animations feel terrible. Even 0.2s tweens massively improve feel.

Available Scripts

MANDATORY: Read the appropriate script before implementing the corresponding pattern.

card_effect_resolution.gd

FILO stack for card effect resolution. Enables reaction/counter cards (last-in resolves first), visual pass for animations, and polymorphic effect dispatch.

Core Loop

1. Draw: Player draws cards from a deck into their hand.
2. Evaluate: Player assesses board state, mana/energy, and card options.
3. Play: Player plays cards to trigger effects (damage, buff, summon).
4. Resolve: Effects occur immediately or go onto a stack.
5. Discard/End: Unused cards are discarded (roguelike) or kept (TCG), turn ends.

Skill Chain

Architecture Overview

1. Card Data (Resource-based)

Godot Resources are perfect for card data.

# card_data.gd
extends Resource
class_name CardData

enum Type { ATTACK, SKILL, POWER }
enum Target { ENEMY, SELF, ALL_ENEMIES }

@export var id: String
@export var name: String
@export_multiline var description: String
@export var cost: int
@export var type: Type
@export var target_type: Target
@export var icon: Texture2D
@export var effect_script: Script # Custom logic per card

2. Deck Manager

Handles the piles: Draw Pile, Hand, Discard Pile, Exhaust Pile.

# deck_manager.gd
var draw_pile: Array[CardData] = []
var hand: Array[CardData] = []
var discard_pile: Array[CardData] = []

func draw_cards(amount: int) -> void:
    for i in amount:
        if draw_pile.is_empty():
            reshuffle_discard()
            
        if draw_pile.is_empty(): 
            break # No cards left
            
        var card = draw_pile.pop_back()
        hand.append(card)
        card_drawn.emit(card)

func reshuffle_discard() -> void:
    draw_pile.append_array(discard_pile)
    discard_pile.clear()
    draw_pile.shuffle()

3. Card Visual (UI)

The interactive node representing a card in hand.

# card_ui.gd
extends Control

var card_data: CardData
var start_pos: Vector2
var is_dragging: bool = false

func _gui_input(event: InputEvent) -> void:
    if event is InputEventMouseButton and event.button_index == MOUSE_BUTTON_LEFT:
        if event.pressed:
            start_drag()
        else:
            end_drag()

func _process(delta: float) -> void:
    if is_dragging:
        global_position = get_global_mouse_position() - size / 2
    else:
        # Hover effect or return to hand position
        pass

Key Mechanics Implementation

Effect Resolution (Command Pattern)

Decouple the "playing" of a card from its "effect".

func play_card(card: CardData, target: Node) -> void:
    if current_energy < card.cost:
        show_error("Not enough energy")
        return
        
    current_energy -= card.cost
    
    # Execute effect
    var effect = card.effect_script.new()
    effect.execute(target)
    
    move_to_discard(card)

Hand Layout (Arching)

Cards in hand usually form an arc. Use a math formula (Bezier or Circle) to position them based on index and total_cards.

func update_hand_visuals() -> void:
    var center_x = screen_width / 2
    var radius = 1000.0
    var angle_step = 5.0
    
    for i in hand_visuals.size():
        var card = hand_visuals[i]
        var angle = deg_to_rad((i - hand_visuals.size() / 2.0) * angle_step)
        var target_pos = Vector2(
            center_x + sin(angle) * radius,
            screen_height + cos(angle) * radius
        )
        card.target_rotation = angle
        card.target_position = target_pos

Common Pitfalls

1. Complexity Overload: Too many keywords. Fix: Stick to 3-5 core keywords (e.g., Taunt, Poison, Shield) and expand slowly.
2. Unreadable Text: Tiny fonts on cards. Fix: Use icons for common stats (Damage, Block) and keep text short.
3. Animation Lock: Waiting for slow animations to finish before playing the next card. Fix: Allow queueing actions or keep animations snappy (< 0.3s).

Godot-Specific Tips

• MouseFilter: Getting drag/drop to work with overlapping UI requires careful setup of mouse_filter (Pass vs Stop).
• Z-Index: Use z_index or CanvasLayer to ensure the dragged card is always on top of everything else.
• Tweens: Essential! Tween position, rotation, and scale for that "juicy" Hearthstone/Slay the Spire feel.

Reference

• Master Skill: godot-master