First commit 🎉

addons/popochiu/engine/interfaces/i_audio.gd

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+class_name PopochiuIAudio
+extends Node
+## Provides access to the [PopochiuAudioCue]s in the game. Access with [b]A[/b] (e.g.
+## [code]A.sfx_woosh.play()[/code]).
+##
+## Interface class that can be used to access all the audio cues in the game in order to play
+## sound effects and music.[br][br]
+## Use examples:[br]
+## [codeblock]
+## func _on_click() -> void:
+##     await A.sfx_tv_on.play()
+##     await E.queue([
+##         A.mx_toon_town.queue_play(),
+##         A.vo_scream.queue_play(true), # Wait for the audio to finish
+##         A.sfx_boing.queue_play(),
+##     ])
+##     A.mx_house.play()
+## [/codeblock]
+
+## Used to convert the value of the pitch set on [member PopochiuAudioCue.pitch] to the
+## corresponding value needed for the [code]pitch_scale[/code] property of the audio stream players.
+var twelfth_root_of_two := pow(2, (1.0 / 12))
+
+
+#region Godot ######################################################################################
+func _init() -> void:
+	Engine.register_singleton(&"A", self)
+
+
+#endregion
+
+#region Public #####################################################################################
+## Transforms [param pitch] to a value that can be used to modify the
+## [member AudioStreamPlayer.pitch_scale] or [member AudioStreamPlayer2D.pitch_scale].
+func semitone_to_pitch(pitch: float) -> float:
+	return pow(twelfth_root_of_two, pitch)
+
+
+## Returns [code]true[/code] if the [PopochiuAudioCue] identified by [param cue_name] is playing.
+func is_playing_cue(cue_name: String) -> bool:
+	return PopochiuUtils.e.am.is_playing_cue(cue_name)
+
+
+#endregion