Add Short songs and a choice of how random songs are picked (#30, #51)

Short songs (#30): a quiz settings switch and a Seconds per song row (30 by
default, 10-120 in steps of 5), saved with the quiz settings. Only part of
each quiz song plays, from a random point 10-60% into it, picked once per song
so restart and repeat play the same part. The progress bar, time and seeking
stay within the part, a hidden beginning counts inside it, and its end counts
as the song ending (repeat, stop or go to the next song as set).

Random songs (#51): the low-played switch in Settings is now a Normal / Low
played / Classic choice, stored as Settings.random_mode and not saved.
fetch_random_song(mode) picks /music/rand, /music/rand/low or
/music/rand/classic.

Closes #30
Closes #51

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

quiz/QuizSettingsCard.tscn

@@ -50,6 +50,49 @@ focus_mode = 0
 action_mode = 0
 text = "Hide next track"
 
+[node name="ShortSongsCheckButton" type="CheckButton" parent="CardPanel/VBox"]
+unique_name_in_owner = true
+layout_mode = 2
+tooltip_text = "Play only a part of each song, from a random point, so more songs fit in a game"
+focus_mode = 0
+action_mode = 0
+text = "Short songs"
+
+[node name="ShortSongSecondsRow" type="HBoxContainer" parent="CardPanel/VBox"]
+unique_name_in_owner = true
+layout_mode = 2
+
+[node name="Title" type="Label" parent="CardPanel/VBox/ShortSongSecondsRow"]
+layout_mode = 2
+size_flags_horizontal = 3
+theme_type_variation = &"SettingsRowLabel"
+text = "Seconds per song"
+
+[node name="ShortSongSecondsLabel" type="Label" parent="CardPanel/VBox/ShortSongSecondsRow"]
+unique_name_in_owner = true
+custom_minimum_size = Vector2(48, 0)
+layout_mode = 2
+text = "30"
+horizontal_alignment = 1
+
+[node name="LowerShortSongSecondsButton" type="Button" parent="CardPanel/VBox/ShortSongSecondsRow"]
+unique_name_in_owner = true
+custom_minimum_size = Vector2(30, 0)
+layout_mode = 2
+focus_mode = 0
+action_mode = 0
+theme_type_variation = &"StepButton"
+text = "-5"
+
+[node name="IncreaseShortSongSecondsButton" type="Button" parent="CardPanel/VBox/ShortSongSecondsRow"]
+unique_name_in_owner = true
+custom_minimum_size = Vector2(30, 0)
+layout_mode = 2
+focus_mode = 0
+action_mode = 0
+theme_type_variation = &"StepButton"
+text = "+5"
+
 [node name="HideBeginningCheckButton" type="CheckButton" parent="CardPanel/VBox"]
 unique_name_in_owner = true
 layout_mode = 2

quiz/quiz_settings_card.gd

@@ -13,6 +13,10 @@ extends BasePopup
 
 ## The most seconds of a song's beginning that can be hidden.
 const MAX_HIDE_SECONDS: float = 10.0
+## The shortest and longest part of a song that Short songs plays, and the step between.
+const MIN_SHORT_SONG_SECONDS: int = 10
+const MAX_SHORT_SONG_SECONDS: int = 120
+const SHORT_SONG_STEP: int = 5
 ## Space between the rows and the card's edges.
 const PADDING: Vector2 = Vector2(16, 12)
 
@@ -21,6 +25,11 @@ const PADDING: Vector2 = Vector2(16, 12)
 @onready var auto_repeat_button: CheckButton = %AutoRepeatCheckButton
 @onready var stop_after_current_button: CheckButton = %StopAfterCurrentCheckButton
 @onready var hide_next_track_button: CheckButton = %HideNextTrackCheckButton
+@onready var short_songs_button: CheckButton = %ShortSongsCheckButton
+@onready var short_song_seconds_row: HBoxContainer = %ShortSongSecondsRow
+@onready var short_song_seconds_label: Label = %ShortSongSecondsLabel
+@onready var lower_short_song_seconds_button: Button = %LowerShortSongSecondsButton
+@onready var increase_short_song_seconds_button: Button = %IncreaseShortSongSecondsButton
 @onready var hide_beginning_button: CheckButton = %HideBeginningCheckButton
 @onready var hide_for_seconds_row: HBoxContainer = %HideForSecondsRow
 @onready var hide_for_seconds_label: Label = %HideForSecondsLabel
@@ -41,6 +50,11 @@ func _ready() -> void:
 	auto_repeat_button.toggled.connect(_save_toggle.bind(&"auto_repeat_song"))
 	stop_after_current_button.toggled.connect(_save_toggle.bind(&"stop_after_current"))
 	hide_next_track_button.toggled.connect(_save_toggle.bind(&"hide_next_track"))
+	short_songs_button.toggled.connect(_on_short_songs_toggled)
+	lower_short_song_seconds_button.pressed.connect(
+			set_short_song_seconds.bind(-SHORT_SONG_STEP, true))
+	increase_short_song_seconds_button.pressed.connect(
+			set_short_song_seconds.bind(SHORT_SONG_STEP, true))
 	hide_beginning_button.toggled.connect(_on_hide_beginning_toggled)
 	hide_length_button.toggled.connect(_save_toggle.bind(&"hide_length"))
 	hide_ticks_button.toggled.connect(_save_toggle.bind(&"hide_ticks"))
@@ -60,6 +74,9 @@ func show_settings() -> void:
 	auto_repeat_button.set_pressed_no_signal(Settings.auto_repeat_song)
 	stop_after_current_button.set_pressed_no_signal(Settings.stop_after_current)
 	hide_next_track_button.set_pressed_no_signal(Settings.hide_next_track)
+	short_songs_button.set_pressed_no_signal(Settings.short_songs)
+	short_song_seconds_row.visible = Settings.short_songs
+	short_song_seconds_label.text = str(Settings.short_song_seconds)
 	hide_beginning_button.set_pressed_no_signal(Settings.hide_beginning)
 	hide_length_button.set_pressed_no_signal(Settings.hide_length)
 	hide_ticks_button.set_pressed_no_signal(Settings.hide_ticks)
@@ -117,6 +134,23 @@ func _save_toggle(on: bool, setting: StringName) -> void:
 	Settings.save_settings()
 
 
+## Sets how many seconds of each song Short songs plays, between
+## [constant MIN_SHORT_SONG_SECONDS] and [constant MAX_SHORT_SONG_SECONDS]. With
+## [param relative] the seconds are added to the current length.
+func set_short_song_seconds(seconds: int, relative: bool = false) -> void:
+	var length: int = Settings.short_song_seconds + seconds if relative else seconds
+	Settings.short_song_seconds = clampi(length, MIN_SHORT_SONG_SECONDS,
+			MAX_SHORT_SONG_SECONDS)
+	short_song_seconds_label.text = str(Settings.short_song_seconds)
+	Settings.save_settings()
+
+
+func _on_short_songs_toggled(on: bool) -> void:
+	_save_toggle(on, &"short_songs")
+	short_song_seconds_row.visible = on
+	_fit_to_rows()
+
+
 func _on_hide_beginning_toggled(on: bool) -> void:
 	_save_toggle(on, &"hide_beginning")
 	hide_for_seconds_row.visible = on

quiz/song_loader.gd

@@ -122,7 +122,7 @@ func _download_random_song(new_song_object: SongObject) -> void:
 			return
 		Playlist.store_song(new_song_object, body)
 		_add_song_to_queue(new_song_object)
-	MusicServerClient.fetch_random_song(Settings.use_low_played_mode, song_downloaded,
+	MusicServerClient.fetch_random_song(Settings.random_mode, song_downloaded,
 			_retry_later.bind(_download_random_song.bind(new_song_object)))