Creating my Go Godot Jam 3 entry devlog 1
IF YOU’RE SEEING THIS, THIS IS A WIP
The jam’s theme is Evolution and all the details are listed here. This time I’m logging as I go, so there might be some changes to the script or scenes along the way I couldn’t actually do this, as I was running out of time.. Note that I’m not going to go into much details, the obvious will be ommitted.
I wanted to do a Snake clone, and I’m using this jam as an excuse to do it and add something to it. The features include:
- Snakes will pass their stats in some form to the next snakes.
- Non-grid snake movement. I just hate the grid constraint, so I wanted to make it move in any direction.
- Depending on the food you eat, you’ll gain new mutations/abilities
and the more you eat the more that mutation develops.didn’t have time to add this feature, sad. - Procedural map creation.
Initial setup
Again, similar to the FlappyBird clone I developed, I’m using the directory structure I wrote about on Godot project structure with slight modifications to test things out. Also using similar Project settings as those from the FlappyBird clone like the pixel art texture imports, keybindings, layers, etc..
I’ve also setup GifMaker, with slight modifications as the AssetLib doesn’t install it correctly and contains unnecessry stuff: moved necessary files to the res://addons directory, deleted test scenes and files in general, and copied the license to the res://docs directory. Setting this up was a bit annoying because the tutorial it’s bad (with all due respect). I might do a separate entry just to explain how to set it up, because I couldn’t find it anywhere other than by inspecting some of the code/scenes.I ended up not leaving this enabled in the game as it lagged the game out, but it’s an option I’ll end up researching more.
This time I’m also going to be using an Event bus singleton (which I’m going to just call Event) as managing signals was pretty annoying on my last project; as well as a Global singleton for essential stuff so I don’t have to do as many cross references between nodes/scenes.
Assets
This time I’ll be creating my own assets in Aseprite, wont be that good, but enough to prototype and get things going.
Other than that I used few key sprites from vryell: Controller & Keyboard Icons and a font from datagoblin: Monogram.
The snake
This is the most challenging part in my opinion as making all the body parts follow the head in a user defined path it’s kinda hard. I tried with like 4-5 options and the one I’m detailing here is the only one that worked as I wanted for me. This time the directory structure I’m using is the following:
Basic movement
The most basic thing is to move the head, this is what we have control of. Create a scene called Head.tscn and setup the basic KinematicBody2D with it’s own Sprite and CollisionShape2D (I used a small circle for the tip of the head), and set the Collision Layer/Mask accordingly, for now just layer = bit 1. And all we need to do, is keep moving the snake forwards and be able to rotate left or right. Created a new script called head.gd attached to the root (KinematicBody2D) and added:
extends KinematicBody2D
enum {
LEFT=-1,
RIGHT=1
}
var velocity: Vector2 = Vector2.ZERO
var _direction: Vector2 = Vector2.UP
func _physics_process(delta: float) -> void:
if Input.is_action_pressed("move_left"):
_rotate_to(LEFT)
if Input.is_action_pressed("move_right"):
_rotate_to(RIGHT)
velocity = _direction * Global.SNAKE_SPEED
velocity = move_and_slide(velocity)
_handle_time_elapsed(delta)
func _rotate_to(direction: int) -> void:
rotate(deg2rad(direction * Global.SNAKE_ROT_SPEED * get_physics_process_delta_time()))
_direction = _direction.rotated(deg2rad(direction * Global.SNAKE_ROT_SPEED * get_physics_process_delta_time()))
After tunning all the necessary parameters you should get something like this:
Setting up path following
To move other snake parts by following the snake head the only solution I found was to use the Path2D and PathFollow2D nodes. Path2D basically just handles the curve/path that PathFollow2D will use to move its child node; and I say “child node” in singular… as PathFollow2D can only handle one damn child, all the other ones will have weird transformations and/or rotations. So, the next thing to do is to setup a way to compute (and draw so we can validate) the snake’s path/curve.
Added the signal snake_path_new_point(coordinates) to the Event singleton and then add the following to head.gd:
var _time_elapsed: float = 0.0
# using a timer is not recommended for < 0.01
func _handle_time_elapsed(delta: float) -> void:
if _time_elapsed >= Global.SNAKE_POSITION_UPDATE_INTERVAL:
Event.emit_signal("snake_path_new_point", global_position)
_time_elapsed = 0.0
_time_elapsed += delta
This will be pinging the current snake head position every 0.01 seconds (defined in Global). Now create a new scene called Snake.tscn which will contain a Node2D, a Path2D and an instance of Head as its childs. Create a new script called snake.gd attached to the root (Node2D) with the following content:
class_name Snake
extends Node2D
onready var path: Path2D = $Path
func _ready():
Event.connect("snake_path_new_point", self, "_on_Head_snake_path_new_point")
func _draw() -> void:
if path.curve.get_baked_points().size() >= 2:
draw_polyline(path.curve.get_baked_points(), Color.aquamarine, 1, true)
func _on_Head_snake_path_new_point(coordinates: Vector2) -> void:
path.curve.add_point(coordinates)
# update call is to draw curve as there are new points to the path's curve
update()
With this, we’re now populating the Path2D curve points with the position of the snake head. You should be able to see it because of the _draw call. If you run it you should see something like this:
Define body parts for the snake
At this point the only thing to do is to add the corresponding next body parts and tail of the snake. To do so, we need a PathFollow2D to use the live-generating Path2D, the only caveat is that we need one of these per body part/tail (this took me hours to figure out, thanks documentation).
Create a new scene called Body.tscn with a PathFollow2D as its root and an Area2D as its child, then just add the necessary Sprite and CollisionShap2D for the Area2D, I’m using layer = bit 2 for its collision. Create a new script called generic_segment.gd with the following code:
extends PathFollow2D
export(String, "body", "tail") var TYPE: String = "body"
func _physics_process(delta: float) -> void:
offset += Global.SNAKE_SPEED * delta
And this can be attached to the Body‘s root node (PathFollow2D), no extra setup needed. Repeat the same steps for creating the Tail.tscn scene and when attaching the generic_segment.gd script just configure the Type parameter to tail in the GUI (by selecting the node with the script attached and editing in the Inspector).
Adding body parts
Now it’s just a matter of handling when to add new body parts in the snake.gd script. For now I’ve only setup for adding body parts to fulfill the initial length of the snake (this doesn’t include the head or tail). The extra code needed is the following:
export(PackedScene) var BODY_SEGMENT_NP: PackedScene
export(PackedScene) var TAIL_SEGMENT_NP: PackedScene
var current_body_segments: int = 0
var max_body_segments: int = 1
func _add_initial_segment(type: PackedScene) -> void:
if path.curve.get_baked_length() >= (current_body_segments + 1.0) * Global.SNAKE_SEGMENT_SIZE:
var _temp_body_segment: PathFollow2D = type.instance()
path.add_child(_temp_body_segment)
current_body_segments += 1
func _on_Head_snake_path_new_point(coordinates: Vector2) -> void:
path.curve.add_point(coordinates)
# update call is to draw curve as there are new points to the path's curve
update()
# add the following lines
if current_body_segments < max_body_segments:
_add_initial_segment(BODY_SEGMENT_NP)
elif current_body_segments == max_body_segments:
_add_initial_segment(TAIL_SEGMENT_NP)
Select the Snake node and add the Body and Tail scene to the parameters, respectively. Then when running you should see something like this:
Now, we need to handle adding body parts after the snake is complete and already moved for a bit, this will require a queue so we can add part by part in the case that we eat multiple pieces of food in a short period of time. For this we need to add some signals: snake_adding_new_segment(type), snake_added_new_segment(type), snake_added_initial_segments and use them when makes sense. Now we need to add the following:
var body_segment_stack: Array
var tail_segment: PathFollow2D
# didn't konw how to name this, basically holds the current path lenght
# whenever the add body segment, and we use this stack to add body parts
var body_segment_queue: Array
As well as updating _add_initial_segment with the following so it adds the new segment on the specific variable:
if _temp_body_segment.TYPE == "body":
body_segment_stack.append(_temp_body_segment)
else:
tail_segment = _temp_body_segment
Now that it’s just a matter of creating the segment queue whenever a new segment is needed, as well as adding each segment in a loop whenever we have items in the queue and it’s a good distance to place the segment on. These two things can be achieved with the following code:
# this will be called in _physics_process
func _add_new_segment() -> void:
var _path_length_threshold: float = body_segment_queue[0] + Global.SNAKE_SEGMENT_SIZE
if path.curve.get_baked_length() >= _path_length_threshold:
var _removed_from_queue: float = body_segment_queue.pop_front()
var _temp_body_segment: PathFollow2D = BODY_SEGMENT_NP.instance()
var _new_body_offset: float = body_segment_stack.back().offset - Global.SNAKE_SEGMENT_SIZE
_temp_body_segment.offset = _new_body_offset
body_segment_stack.append(_temp_body_segment)
path.add_child(_temp_body_segment)
tail_segment.offset = body_segment_stack.back().offset - Global.SNAKE_SEGMENT_SIZE
current_body_segments += 1
func _add_segment_to_queue() -> void:
# need to have the queues in a fixed separation, else if the eating functionality
# gets spammed, all next bodyparts will be spawned almost at the same spot
if body_segment_queue.size() == 0:
body_segment_queue.append(path.curve.get_baked_length())
else:
body_segment_queue.append(body_segment_queue.back() + Global.SNAKE_SEGMENT_SIZE)
With everything implemented and connected accordingly then we can add segments on demand (for testing I’m adding with a keystroke), it should look like this:
For now, this should be enough, I’ll add more stuff as needed as I go. Last thing is that after finished testing that the movement felt ok, I just added a way to stop the snake whenever it collides with itself by using the following code (and the signal snake_segment_body_entered(body)) in a main.gd script that is the entry point for the game:
func _snake_disabled(on_off: bool) -> void:
_snake.propagate_call("set_process", [on_off])
_snake.propagate_call("set_process_internal", [on_off])
_snake.propagate_call("set_physics_process", [on_off])
_snake.propagate_call("set_physics_process_internal", [on_off])
_snake.propagate_call("set_process_input", [on_off])
Which will stop the snake node and all children.
Fix on body segments following head
After a while of testing and developing, I noticed that sometimes the head “detaches” from the body when a lot of rotations happen (moving the snake left or right), because of how imprecise the Curve2D is. To do this I just send a signal (snake_rotated) whenever the snake rotates and make a small correction (in generic_segment.gd):
func _on_snake_rotated() -> void:
offset -= 0.75 * Global.SNAKE_SPEED * pow(get_physics_process_delta_time(), 2)
This is completely random, I tweaked it manually after a lot of iterations.
The food
For now I just decided to setup a simple system to see everything works fine. The idea is to make some kind of generic food node/scene and a “food manager” to spawn them, for now in totally random locations. For this I added the following signals: food_placing_new_food(type), food_placed_new_food(type) and food_eaten(type).
First thing is creating the Food.tscn which is just an Area2D with its necessary children with an attached script called food.gd. The script is really simple:
class_name Food # needed to access Type enum outside of the script, this registers this script as a node
extends Area2D
enum Type {
APPLE
}
var _type_texture: Dictionary = {
Type.APPLE: preload("res://entities/food/sprites/apple.png")
}
export(Type) var TYPE
onready var _sprite: Sprite = $Sprite
func _ready():
connect("body_entered", self, "_on_body_entered")
_sprite.texture = _type_texture[TYPE]
func _on_body_entered(body: Node) -> void:
Event.emit_signal("food_eaten", TYPE)
queue_free()
Then this food_eaten signal is received in snake.gd to add a new segment to the queue.
Finally, for the food manager I just created a FoodManager.tscn with a Node2D with an attached script called food_manager.gd. To get a random position:
func _get_random_pos() -> Vector2:
var screen_size: Vector2 = get_viewport().get_visible_rect().size
var temp_x: float = randf() * screen_size.x - screen_size.x / 2.0
var temp_y: float = randf() * screen_size.y - screen_size.y / 2.0
return Vector2(temp_x, temp_y)
Which gets the job done, but later I’ll have to add a way to check that the position is valid. And to actually place the food:
func _place_new_food() -> void:
var food: Area2D = FOOD.instance()
var position: Vector2 = _get_random_pos()
food.global_position = position
add_child(food)
And this is used in _process to place new food whenever needed. For now I added a condition to add food until 10 pieces are in place, and keep adding whenever the food is is lower than 10. After setting everything up, this is the result:
Za warudo! (The world)
It just happend that I saw a video to create random maps by using a method called random walks, this video was made by NAD LABS: Nuclear Throne Like Map Generation In Godot. It’s a pretty simple but powerful script, he provided the source code from which I based my random walker, just tweaked a few things and added others. Some of the maps than can be generated with this method (already aded some random sprites):
It started with just black and white tiles, but I ended up adding some sprites as it was really harsh to the eyes. My implementation is basically the same as NAD LABS‘ with few changes, most importantly: I separated the generation in 2 diferent tilemaps (floor and wall) to have better control as well as wrapped everything in a single scene with a “main” script with the following important functions:
func get_valid_map_coords() -> Array:
var safe_area: Array = walker_head.get_cells_around()
var cells_used: Array = ground_tilemap.get_used_cells()
for location in safe_area:
cells_used.erase(location)
return cells_used
func get_centered_world_position(location: Vector2) -> Vector2:
return ground_tilemap.map_to_world(location) + Vector2.ONE * Global.TILE_SIZE / 2.0
Where get_cells_around is just a function that gets the safe cells around the origin. And this get_valid_map_coords just returns used cells minus the safe cells, to place food. get_centered_world_position is so we can center the food in the tiles.
Some signals I used for the world gen: world_gen_walker_started(id), world_gen_walker_finished(id), world_gen_walker_died(id) and world_gen_spawn_walker_unit(location).
Food placement
The last food algorithm doesn’t check anything related to the world, and thus the food could spawn in the walls and outside the map.
First thing is I generalized the food into a single script and added basic food and special food which inherit from base food. The most important stuff for the base food is to be able to set all necessary properties at first:
func update_texture() -> void:
_sprite.texture = texture[properties["type"]]
func set_properties(pos: Vector2, loc: Vector2, special: bool, type: int, points: int=1, special_points: int=1, ttl: float = -1.0) -> void:
properties["global_position"] = pos
global_position = pos
properties["location"] = loc
properties["special"] = special
properties["type"] = type
properties["points"] = points
properties["special_points"] = special_points
properties["ttl"] = ttl
if properties["ttl"] != -1.0:
timer.wait_time = properties["ttl"]
timer.start()
Where the update_texture needs to be a separate function, because we need to create the food first, set properties, add as a child and then update the sprite; we also need to keep track of the global position, location (in tilemap coordinates) and identifiers for the type of food.
Then basic/special food just extend base food, define a Type enum and preloads the necessary textures, for example:
enum Type {
APPLE,
BANANA,
RAT
}
func _ready():
texture[Type.APPLE] = preload("res://entities/food/sprites/apple.png")
texture[Type.BANANA] = preload("res://entities/food/sprites/banana.png")
texture[Type.RAT] = preload("res://entities/food/sprites/rat.png")
Now, some of the most important change to food_manager.gd is to get an actual random valid position:
func _get_random_pos() -> Array:
var found_valid_loc: bool = false
var index: int
var location: Vector2
while not found_valid_loc:
index = randi() % possible_food_locations.size()
location = possible_food_locations[index]
if current_basic_food.find(location) == -1 and current_special_food.find(location) == -1:
found_valid_loc = true
return [world_generator.get_centered_world_position(location), location]
Other than that, there are some differences between placing normal and special food (specially the signal they send, and if an extra “special points” property is set). Some of the signals that I used that might be important: food_placing_new_food(type), food_placed_new_food(type, location) and food_eaten(type, location).
TODO
Add notes on:
- Score manager stuff.
- Saved data and
Statsclass. - State machine for player regarding abilities.
Other minor stuff
Not as important but worth mentioning:
- Added restartability function.
- Added signals for game control:
game_overandgame_start, but ended not using them. - Fixed issue where the Curve2D stayed the same even when restarting by just setting an empty curve on starting the node.
- Added a debug mode for drawing of the Curve2D instead of always drawing.
- Tweaked the tracking of the snake size.
- Tweaked the food system to contain more attributes and use a base food node.
- Added a HUD with mini snake sprites.
- Added a HUD for growth progress on snake body segments and abilities.
- Refactored the nodes to make it work with
change_scene_to, and added a main menu. - Added GUI for dead screen, showing the progress.
By David Luévano
Created: Wed, Jun 08, 2022 @ 08:26 UTC