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The main game scene

Now it's time to bring everything we did together into a playable game scene.

Create a new scene and add a Node named Main. (The reason we are using Node instead of Node2D is because this node will be a container for handling game logic. It does not require 2D functionality itself.)

Click the Instance button (represented by a chain link icon) and select your saved player.tscn.

../../_images/instance_scene.webp

Ora, aggiungi i seguenti nodi come figli di Main, e rinominali come mostrato (i valori sono in secondi):

  • Timer (chiamato MobTimer) - per controllare la frequenza con cui i mob si generano

  • Timer (chiamato ScoreTimer) - per incrementare il punteggio ogni secondo

  • Timer (chiamato StartTimer) - per dare un ritardo prima di iniziare

  • Marker2D (named StartPosition) - to indicate the player's start position

Imposta la proprietà Wait Time di ciascuno dei nodi Timer come segue:

  • MobTimer: 0.5

  • ScoreTimer: 1

  • StartTimer: 2

In addition, set the One Shot property of StartTimer to "On" and set Position of the StartPosition node to (240, 450).

Generazione dei Mostri

Il nodo Main genererà nuovi mob, e vogliamo che appaiano in una posizione casuale sul bordo dello schermo. Aggiungi un nodo Path2D chiamato MobPath come figlio di Main. Quando selezioni Path2D, vedrai alcuni nuovi pulsanti nella parte superiore dell'editor:

../../_images/path2d_buttons.webp

Select the middle one ("Add Point") and draw the path by clicking to add the points at the corners shown. To have the points snap to the grid, make sure "Use Grid Snap" and "Use Smart Snap" are both selected. These options can be found to the left of the "Lock" button, appearing as a magnet next to some dots and intersecting lines, respectively.

../../_images/grid_snap_button.webp

Importante

Disegna il percorso in ordine orario, o i tuoi nemici verranno generati verso l'esterno invece che verso l'interno!

../../_images/draw_path2d.gif

Dopo aver posizionato il punto 4 nell'immagine, fare clic sul pulsante "Chiudi curva" e la curva sarà completa.

Ora che il percorso è definito, aggiungere un nodo :ref:'PathFollow2D <class_PathFollow2D>' come figlio di ''MobPath'' e denominarlo ''MobSpawnLocation''. Questo nodo ruoterà automaticamente e seguirà il percorso mentre si muove, quindi possiamo usarlo per selezionare una posizione e una direzione casuali lungo il percorso.

La tua scena dovrebbe assomigliare a questa:

../../_images/main_scene_nodes.webp

Script principale

Add a script to Main. At the top of the script, we use @export var mob_scene: PackedScene to allow us to choose the Mob scene we want to instance.

extends Node

@export var mob_scene: PackedScene
var score

Click the Main node and you will see the Mob Scene property in the Inspector under "Script Variables".

Puoi assegnare il valore di questa proprietà in due modi:

  • Drag mob.tscn from the "FileSystem" dock and drop it in the Mob Scene property.

  • Click the down arrow next to "[empty]" and choose "Load". Select mob.tscn.

Next, select the instance of the Player scene under Main node in the Scene dock, and access the Node dock on the sidebar. Make sure to have the Signals tab selected in the Node dock.

You should see a list of the signals for the Player node. Find and double-click the hit signal in the list (or right-click it and select "Connect..."). This will open the signal connection dialog. We want to make a new function named game_over, which will handle what needs to happen when a game ends. Type "game_over" in the "Receiver Method" box at the bottom of the signal connection dialog and click "Connect". You are aiming to have the hit signal emitted from Player and handled in the Main script. Add the following code to the new function, as well as a new_game function that will set everything up for a new game:

func game_over():
    $ScoreTimer.stop()
    $MobTimer.stop()

func new_game():
    score = 0
    $Player.start($StartPosition.position)
    $StartTimer.start()

Now connect the timeout() signal of each of the Timer nodes (StartTimer, ScoreTimer, and MobTimer) to the main script. StartTimer will start the other two timers. ScoreTimer will increment the score by 1.

func _on_score_timer_timeout():
    score += 1

func _on_start_timer_timeout():
    $MobTimer.start()
    $ScoreTimer.start()

In _on_mob_timer_timeout(), we will create a mob instance, pick a random starting location along the Path2D, and set the mob in motion. The PathFollow2D node will automatically rotate as it follows the path, so we will use that to select the mob's direction as well as its position. When we spawn a mob, we'll pick a random value between 150.0 and 250.0 for how fast each mob will move (it would be boring if they were all moving at the same speed).

Nota che una nuova istanza deve essere aggiunta alla scena usando add_child().

func _on_mob_timer_timeout():
    # Create a new instance of the Mob scene.
    var mob = mob_scene.instantiate()

    # Choose a random location on Path2D.
    var mob_spawn_location = get_node("MobPath/MobSpawnLocation")
    mob_spawn_location.progress_ratio = randf()

    # Set the mob's direction perpendicular to the path direction.
    var direction = mob_spawn_location.rotation + PI / 2

    # Set the mob's position to a random location.
    mob.position = mob_spawn_location.position

    # Add some randomness to the direction.
    direction += randf_range(-PI / 4, PI / 4)
    mob.rotation = direction

    # Choose the velocity for the mob.
    var velocity = Vector2(randf_range(150.0, 250.0), 0.0)
    mob.linear_velocity = velocity.rotated(direction)

    # Spawn the mob by adding it to the Main scene.
    add_child(mob)

Importante

Why PI? In functions requiring angles, Godot uses radians, not degrees. Pi represents a half turn in radians, about 3.1415 (there is also TAU which is equal to 2 * PI). If you're more comfortable working with degrees, you'll need to use the deg_to_rad() and rad_to_deg() functions to convert between the two.

Testare la scena

Let's test the scene to make sure everything is working. Add this new_game call to _ready():

func _ready():
    new_game()

Let's also assign Main as our "Main Scene" - the one that runs automatically when the game launches. Press the "Play" button and select main.tscn when prompted.

Suggerimento

If you had already set another scene as the "Main Scene", you can right click main.tscn in the FileSystem dock and select "Set As Main Scene".

Dovresti essere in grado di muovere il giocatore, vedere i nemici che vengono generati e vedere il giocatore scomparire quando viene colpito da uno di essi.

Quando sei sicuro che tutto funzioni, rimuovi la chiamata a new_game() da _ready().

What's our game lacking? Some user interface. In the next lesson, we'll add a title screen and display the player's score.