player: Add "glide" special ability

If the player holds down the "jump" action, their character's downwards
speed is capped to a constant. This allows the player-character to
travel across wider gaps by jumping then gliding.

The function call for this ability is in _physics_process(), after other
"normal" adjustments to the velocity but before move_and_slide().
However, it is commented out. A learner must find this commented-out
line and uncomment it to enable this ability.

The sound effect is from
https://freesound.org/people/tothrec2/sounds/596541/, licensed under
CC0-1.0.

Author: wjt

assets/sounds/596541__tothrec2__large-wings-flapping-foley.ogg

@@ -0,0 +1,19 @@
+[remap]
+
+importer="oggvorbisstr"
+type="AudioStreamOggVorbis"
+uid="uid://p0b3e0t7h8j3"
+path="res://.godot/imported/596541__tothrec2__large-wings-flapping-foley.ogg-715998e9d4f908348de867f3ceb6fce5.oggvorbisstr"
+
+[deps]
+
+source_file="res://assets/sounds/596541__tothrec2__large-wings-flapping-foley.ogg"
+dest_files=["res://.godot/imported/596541__tothrec2__large-wings-flapping-foley.ogg-715998e9d4f908348de867f3ceb6fce5.oggvorbisstr"]
+
+[params]
+
+loop=false
+loop_offset=0
+bpm=0
+beat_count=0
+bar_beats=4

assets/sounds/596541__tothrec2__large-wings-flapping-foley.ogg.import

@@ -1,8 +1,9 @@
-[gd_scene load_steps=8 format=3 uid="uid://8st4scqt06l8"]
+[gd_scene load_steps=9 format=3 uid="uid://8st4scqt06l8"]
 
 [ext_resource type="Script" uid="uid://umb21eb2y1oj" path="res://scripts/player.gd" id="1_w3ms2"]
 [ext_resource type="SpriteFrames" uid="uid://bo581k1esb50n" path="res://components/player/spriteframes-red.tres" id="2_msaml"]
 [ext_resource type="AudioStream" uid="uid://bx1joarpc14j5" path="res://assets/sounds/538066__stevielematt__boing.ogg" id="3_wa6cj"]
+[ext_resource type="AudioStream" uid="uid://p0b3e0t7h8j3" path="res://assets/sounds/596541__tothrec2__large-wings-flapping-foley.ogg" id="4_mpawu"]
 
 [sub_resource type="CapsuleShape2D" id="CapsuleShape2D_7x5a4"]
 radius = 31.0
@@ -51,3 +52,7 @@ one_way_collision = true
 [node name="JumpSFX" type="AudioStreamPlayer" parent="SoundEffects"]
 unique_name_in_owner = true
 stream = SubResource("AudioStreamRandomizer_mpawu")
+
+[node name="GlideSFX" type="AudioStreamPlayer" parent="SoundEffects"]
+unique_name_in_owner = true
+stream = ExtResource("4_mpawu")

components/player/player.tscn

@@ -3,6 +3,12 @@ class_name Player
 extends CharacterBody2D
 ## A player's character, which can walk, jump, and stomp on enemies.
 
+## The player-character's maximum downwards speed while gliding.
+## Making this number smaller allows the player to glide further.
+## [br][br]
+## Used by [method _glide].
+const GLIDE_TERMINAL_VELOCITY = 100
+
 ## Which player controls this character?
 @export var player: Global.Player = Global.Player.ONE
 
@@ -57,6 +63,7 @@ var original_position: Vector2
 @onready var _double_jump_particles: CPUParticles2D = %DoubleJumpParticles
 
 @onready var _jump_sfx: AudioStreamPlayer = %JumpSFX
+@onready var _glide_sfx: AudioStreamPlayer = %GlideSFX
 
 
 func _set_sprite_frames(new_sprite_frames):
@@ -106,6 +113,21 @@ func stomp():
 	_jump()
 
 
+## If the player-character is in the air, and the "jump" action is held, clamp the downwards
+## velocity to a constant. Must be called after applying gravity to the player-character.
+func _glide() -> void:
+	if not is_on_floor() and Input.is_action_pressed(Actions.lookup(player, "jump")):
+		if velocity.y > GLIDE_TERMINAL_VELOCITY:
+			velocity.y = GLIDE_TERMINAL_VELOCITY
+
+		# Only play the sound effect when the player-character is moving downwards, not while
+		# jumping upwards
+		if velocity.y > 0 and not _glide_sfx.playing:
+			_glide_sfx.play()
+	elif _glide_sfx.playing:
+		_glide_sfx.stop()
+
+
 func _physics_process(delta):
 	# Don't move if there are no lives left.
 	if Global.lives <= 0:
@@ -142,6 +164,8 @@ func _physics_process(delta):
 	else:
 		velocity.x = move_toward(velocity.x, 0, acceleration * delta)
 
+	# _glide()
+
 	if velocity == Vector2.ZERO:
 		_sprite.play("idle")
 	else: