Turn System

Turn order calculation, action points, phase management, and timeline systems define turn-based combat.

NEVER Do (Expert Anti-Patterns)

Order & Determinism

• NEVER recalculate turn order every action; strictly sort once per round or ONLY when a speed-relevant stat changes to prevent O(n log n) lag.

• NEVER use random tie-breaking for initiative; strictly use a secondary static attribute (Agility, ID, or persistent "luck") for deterministic replays.

• NEVER modify an active turn-order queue while iterating it; strictly iterate over a duplicate() or apply queue modifications after the loop.

• NEVER broadcast global turn state changes using immediate call_group(); strictly use call_group_flags(SceneTree.GROUP_CALL_DEFERRED, ...) to prevent frame spikes when notifying hundreds of units.

• NEVER rely on the Node hierarchy as the source of truth; strictly use a Dictionary board state for logical grid coordinates.

Logic & Action Economy

• NEVER deduct Action Points (AP) before validation; strictly call can_perform_action(cost) before applying current_ap -= cost to prevent exploits.
• NEVER hardcode phase transitions (if phase == 0); strictly use an enum + match or a dedicated State Machine for Draw/Main/End phases.
• NEVER emit "Turn Ended" before internal cleanup; strictly reset AP and tick status effects BEFORE signaling the next turn.
• NEVER use exact floating-point equality (==) for AP checks; strictly use >= or is_equal_approx() for robust comparisons.

Tactical Grid & UI

• NEVER use generic AStar2D for tile grids; strictly use AStarGrid2D for 10x faster pathfinding and native diagonal handling.
• NEVER forget to call update() on AStarGrid2D after changing obstacle states; if you toggle set_point_solid(), the grid MUST refresh before the next query.
• NEVER lock the main thread with while loops for input; strictly use the await keyword or signals to yield execution back to the Tree.
• NEVER handle turn decisions with is_action_pressed(); strictly use is_action_just_pressed() for discrete, frame-locked menu input.
• NEVER skip turn timeouts in networked games; strictly implement a server-side timer with a default "pass" action to prevent griefing.

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🛠 Expert Components (scripts/)

Original Expert Patterns

• active_time_battle.gd - Framework for ATB systems with dynamic progress bars and async action support.
• timeline_turn_manager.gd - Advanced manager for timeline-based turns with interrupts and predictive visualization.

Modular Components

• turn_system_patterns.gd - Collection of patterns for match state machines, UndoRedo, and A* Grid setup.

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# turn_manager.gd (AutoLoad)
extends Node

signal turn_started(combatant: Node)
signal turn_ended(combatant: Node)
signal round_ended

var combatants: Array[Node] = []
var turn_order: Array[Node] = []
var current_turn_index: int = 0

func start_combat(participants: Array[Node]) -> void:
    combatants = participants
    calculate_turn_order()
    start_next_turn()

func calculate_turn_order() -> void:
    turn_order = combatants.duplicate()
    turn_order.sort_custom(func(a, b): return a.speed > b.speed)

func start_next_turn() -> void:
    if current_turn_index >= turn_order.size():
        current_turn_index = 0
        round_ended.emit()
        calculate_turn_order()  # Recalculate each round
    
    var current := turn_order[current_turn_index]
    turn_started.emit(current)

func end_turn() -> void:
    var current := turn_order[current_turn_index]
    turn_ended.emit(current)
    current_turn_index += 1
    start_next_turn()

Action Point System

# combatant.gd
extends Node

@export var max_action_points: int = 3
var current_action_points: int = 3

func start_turn() -> void:
    current_action_points = max_action_points

func can_perform_action(cost: int) -> bool:
    return current_action_points >= cost

func perform_action(cost: int) -> bool:
    if not can_perform_action(cost):
        return false
    
    current_action_points -= cost
    return true

Turn Phases

enum Phase { DRAW, MAIN, END }

var current_phase: Phase = Phase.DRAW

func advance_phase() -> void:
    match current_phase:
        Phase.DRAW:
            current_phase = Phase.MAIN
        Phase.MAIN:
            current_phase = Phase.END
        Phase.END:
            TurnManager.end_turn()
            current_phase = Phase.DRAW

Best Practices

1. Speed-Based - Initiative determines order
2. Action Points - Limit actions per turn
3. Timeout - Add turn timer for online play

Reference

• Related: godot-combat-system, godot-rpg-stats

Related

• Master Skill: godot-master