Genre: Metroidvania

Expert blueprint for Metroidvanias balancing exploration, progression, and backtracking rewards.

NEVER Do (Expert Anti-Patterns)

World Design & Exploration

• NEVER allow "Soft-Locks" where a player is trapped; if they enter via a one-way path ("valve"), they MUST be able to leave using current abilities. Always design fail-safe escape routes.
• NEVER create empty dead ends; if a player backtracks to a remote area, they MUST be rewarded with a collectible, lore, or currency. Empty rooms are design failures.
• NEVER make backtracking purely repetitive; as the player gains movement (Dash/Teleport), traversal through old areas MUST become faster. Open shortcuts to bypass long, early routes.
• NEVER hide the critical path without "crumbs"; use distinct Landmarks, unique lighting, or environmental storytelling to build the player's mental map.
• NEVER design abilities that serve only one purpose; strictly implement dual-use traversal and combat functionality (e.g., a "Dash" that crosses gaps and dodges attacks).

Persistence & Mapping

• NEVER forget to save persistent room state; if a player opens a chest or defeats a boss, that state MUST remain saved when they leave and return.
• NEVER load interconnected rooms synchronously via load(); strictly use ResourceLoader.load_threaded_request() for seamless transitions.
• NEVER track global progression within localized room scripts; strictly use Autoload Singletons for global ability flags and world state.
• NEVER use floating-point types for grid coordinates (minimaps/fog); strictly use Vector2i to prevent precision jitter.
• NEVER manipulate the SceneTree directly from a background loading thread; strictly use call_deferred().

Physics & Controls

• NEVER calculate jump arcs or dashes inside _process(); strictly use _physics_process() to prevent stutter.
• NEVER multiply CharacterBody2D velocity by delta before move_and_slide(); the engine handles this internally.
• NEVER poll is_action_just_pressed() inside _physics_process() for buffering; strictly capture events in _unhandled_input().
• NEVER use standard strings for high-frequency ability checks; strictly use StringName (&"dashing") for pointer-speed comparisons.
• NEVER iterate through every node to broadcast updates; strictly use SceneTree.call_group() for efficient mass communication.
• NEVER delete active room/player nodes via free(); strictly use queue_free() to avoid segmentation faults.

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🛠 Expert Components (scripts/)

Original Expert Patterns

• minimap_fog.gd - Grid-based fog of war that tracks visited rooms and persists via global save data.
• progression_gate_manager.gd - Central manager for ability-gated progression (Locks/Keys) and world persistence.

Modular Components

• platformer_jump_buffer.gd - Modular coyote time and jump buffering for high-fidelity movement.
• background_room_streamer.gd - Thread-safe background room preloading using ResourceLoader.
• safe_scene_switcher.gd - Deferred scene transition pattern for stable cross-room world-state switching.
• minimap_fog_revealer.gd - Vector2i-based fog-of-war clearing logic synced to player position.
• persistent_progression_system.gd - Autoload pattern for tracking global ability/collectible flags.
• ability_state_machine.gd - Optimized StringName pattern matching for traversal/combat states.
• fast_wall_detector.gd - Direct PhysicsServer queries for performance-optimized wall detection.
• save_station_broadcast.gd - Group-based entity resetting and healing logic on save interaction.
• decoupled_hazard_logic.gd - Interface-style pattern for generic damage interaction.
• smooth_room_camera_transition.gd - Tween-based camera limit interpolation for seamless room movement.

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Core Loop

1. Exploration: Player explores available rooms until blocked by a "lock" (obstacle).
2. Discovery: Player finds a "key" (ability/item) or boss.
3. Acquisition: Player gains new traversal or combat ability.
4. Backtracking: Player returns to previous locks with new ability.
5. Progression: New areas open up, cycle repeats.

Skill Chain

Phase	Skills	Purpose
1. Character	godot-characterbody-2d, state-machines	Tight, responsive movement (Coyote time, buffers)
2. World	godot-tilemap-mastery, level-design	Interconnected map, biomes, landmarks
3. Systems	godot-save-load-systems, godot-scene-management	Persistent world state, room transitions
4. UI	ui-system, godot-inventory-system	Map system, inventory, HUD
5. Polish	juiciness	Effects, atmosphere, environmental storytelling

Architecture Overview

1. Game State & Persistence

Metroidvanias require tracking the state of every collectible and boss across the entire world.

# game_state.gd (AutoLoad)
extends Node

var collected_items: Dictionary = {} # "room_id_item_id": true
var unlocked_abilities: Array[String] = []
var map_visited_rooms: Array[String] = []

func register_collectible(id: String) -> void:
    collected_items[id] = true
    save_game()

func has_ability(ability_name: String) -> bool:
    return ability_name in unlocked_abilities

2. Room Transitions

Seamless transitions are key. Use a SceneManager to handle instancing new rooms and positioning the player.

# door.gd
extends Area2D

@export_file("*.tscn") var target_scene_path: String
@export var target_door_id: String

func _on_body_entered(body: Node2D) -> void:
    if body.is_in_group("player"):
        SceneManager.change_room(target_scene_path, target_door_id)

3. Ability System (State Machine Integration)

Abilities should be integrated into the player's State Machine.

# player_state_machine.gd
func _physics_process(delta):
    if Input.is_action_just_pressed("jump") and is_on_floor():
        transition_to("Jump")
    elif Input.is_action_just_pressed("jump") and not is_on_floor() and GameState.has_ability("double_jump"):
        transition_to("DoubleJump")
    elif Input.is_action_just_pressed("dash") and GameState.has_ability("dash"):
        transition_to("Dash")

Key Mechanics Implementation

Map System

A grid-based or node-based map is essential for navigation.

• Grid Map: Auto-fill cells based on player position.
• Room State: Track "visited" status to reveal map chunks.

# map_system.gd
func update_map(player_pos: Vector2) -> void:
    var grid_pos = local_to_map(player_pos)
    if not grid_map_data.has(grid_pos):
        grid_map_data[grid_pos] = VISITED
        ui_map.reveal_cell(grid_pos)

Ability Gating (The "Lock")

Obstacles that check for specific abilities.

# breakable_wall.gd
extends StaticBody2D

@export var required_ability: String = "super_missile"

func take_damage(amount: int, ability_type: String) -> void:
    if ability_type == required_ability:
        destroy()
    else:
        play_deflect_sound()

Common Pitfalls

1. Softlocks: Ensure the player cannot get stuck in an area without the ability to leave. Design "valves" (one-way drops) carefully.
2. Backtracking Tedium: Make backtracking interesting by changing enemies, opening shortcuts, or making traversal faster with new abilities.
3. Empty Rewards: Every dead end should have a reward (health upgrade, lore, currency).
4. Lost Players: Use visual landmarks and environmental storytelling to guide players without explicit markers (e.g., "The Statue Room").

Godot-Specific Tips

• Camera2D: Use limit_left, limit_top, etc., to confine the camera to the current room bounds. Update these limits on room transition.
• Resource Preloading: Preload adjacent rooms for seamless open-world feel if not using hard transitions.
• RemoteTransform2D: Use this to have the camera follow the player but stay detached from the player's rotation/scale.
• TileMap Layers: Use separate layers for background (parallax), gameplay (collisions), and foreground (visual depth).

Design Principles (from Dreamnoid)

• Ability Versatility: Abilities should serve both traversal and combat (e.g., a dash that dodges attacks and crosses gaps).
• Practice Rooms: Introduce a mechanic in a safe environment before testing the player in a dangerous one.
• Landmarks: Distinct visual features help players build a mental map.
• Item Descriptions: Use them for "micro-stories" to build lore without interrupting gameplay.

Reference

• Master Skill: godot-master