/**** 
* Plugins
****/ 
var tween = LK.import("@upit/tween.v1");
var storage = LK.import("@upit/storage.v1", {
	language: "en"
});

/**** 
* Classes
****/ 
// Note types: 'tap', 'hold', 'swipe'
var Note = Container.expand(function () {
	var self = Container.call(this);
	self.type = 'tap'; // tap, hold, swipe
	self.lane = 0; // 0-3
	self.time = 0; // ms, when the note should be hit
	self.duration = 0; // for hold notes, ms
	self.hit = false;
	self.active = true;
	self.swipeDir = null; // 'left', 'right', 'up', 'down' for swipe notes
	// Visuals
	self.noteAsset = null;
	self.trailAsset = null;
	self.init = function (type, lane, time, duration, swipeDir) {
		self.type = type;
		self.lane = lane;
		self.time = time;
		self.duration = duration || 0;
		self.swipeDir = swipeDir || null;
		self.hit = false;
		self.active = true;
		if (self.noteAsset) {
			self.removeChild(self.noteAsset);
		}
		if (self.trailAsset) {
			self.removeChild(self.trailAsset);
		}
		if (type === 'tap') {
			self.noteAsset = self.attachAsset('tapNote', {
				anchorX: 0.5,
				anchorY: 0.5
			});
		} else if (type === 'hold') {
			self.trailAsset = self.attachAsset('noteTrail', {
				anchorX: 0.5,
				anchorY: 1
			});
			self.noteAsset = self.attachAsset('holdNote', {
				anchorX: 0.5,
				anchorY: 0.5
			});
		} else if (type === 'swipe') {
			self.noteAsset = self.attachAsset('swipeNote', {
				anchorX: 0.5,
				anchorY: 0.5
			});
		}
	};
	self.setTrailLength = function (len) {
		if (self.trailAsset) {
			self.trailAsset.height = len;
		}
	};
	self.flash = function () {
		if (self.noteAsset) {
			tween(self.noteAsset, {
				alpha: 0.2
			}, {
				duration: 80,
				onFinish: function onFinish() {
					tween(self.noteAsset, {
						alpha: 1
					}, {
						duration: 80
					});
				}
			});
		}
	};
	self.update = function () {
		// Position is handled by main game loop
	};
	return self;
});
// Song selection card
var SongCard = Container.expand(function () {
	var self = Container.call(this);
	self.songId = '';
	self.cover = null;
	self.init = function (songId, colorAsset) {
		self.songId = songId;
		if (self.cover) {
			self.removeChild(self.cover);
		}
		if (colorAsset) {
			self.cover = self.attachAsset(colorAsset, {
				anchorX: 0.5,
				anchorY: 0.5
			});
		}
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x181c20
});

/**** 
* Game Code
****/ 
// --- GLOBALS ---
// Note: Assets are auto-initialized by LK based on usage below.
// We'll use shapes for notes, and images for backgrounds and song covers as needed.
// Example note assets:
// Sounds and music (placeholders, actual music not implemented here)
var GAME_STATE = 'LANGUAGE'; // LANGUAGE, HOME, STORY, DIFFICULTY, PLAY, RESULT
var selectedLanguage = storage.language || 'en';
var selectedSong = null;
var selectedDifficulty = null;
var currentSongData = null;
var currentNotes = [];
var noteIndex = 0;
var startTime = 0;
var score = 0;
var combo = 0;
var maxCombo = 0;
var accuracy = 0;
var totalNotes = 0;
var hitNotes = 0;
var missNotes = 0;
var holdActive = null;
var swipeStart = null;
var swipeNote = null;
var isPlaying = false;
var resultTimeout = null;
// Lanes: 4 lanes, evenly spaced
var LANE_COUNT = 4;
var LANE_WIDTH = 400;
var LANE_MARGIN = 40;
var LANE_START_X = (2048 - (LANE_COUNT * LANE_WIDTH + (LANE_COUNT - 1) * LANE_MARGIN)) / 2;
var HIT_LINE_Y = 2200; // Where notes should be hit
// --- SONG DATA (MVP: 3 songs, 3 difficulties, simple patterns) ---
var SONGS = [{
	id: 'sky_journey',
	title: 'Sky Journey',
	cover: 'songCover1',
	story: {
		en: "You soar above the clouds, chasing the horizon. The sky is endless, and your journey has just begun.",
		zh: "你在云端翱翔，追逐地平线。天空无垠，你的旅程才刚刚开始。"
	},
	difficulties: ['Easy', 'Medium', 'Hard'],
	notes: {
		Easy: [
		// [type, lane, time(ms), duration(ms), swipeDir]
		['tap', 0, 1000], ['tap', 1, 1800], ['tap', 2, 2600], ['tap', 3, 3400], ['hold', 1, 4200, 1200], ['tap', 0, 6000], ['swipe', 2, 7000, 0, 'right'], ['tap', 3, 8000]],
		Medium: [['tap', 0, 800], ['tap', 1, 1400], ['tap', 2, 2000], ['tap', 3, 2600], ['hold', 0, 3200, 1000], ['tap', 1, 4400], ['swipe', 2, 5200, 0, 'left'], ['tap', 3, 6000], ['tap', 2, 6600], ['hold', 1, 7200, 1200], ['tap', 0, 9000]],
		Hard: [['tap', 0, 600], ['tap', 1, 1000], ['tap', 2, 1400], ['tap', 3, 1800], ['hold', 0, 2200, 1000], ['tap', 1, 3400], ['swipe', 2, 3800, 0, 'up'], ['tap', 3, 4200], ['tap', 2, 4600], ['hold', 1, 5000, 1200], ['tap', 0, 6400], ['swipe', 3, 7000, 0, 'down'], ['tap', 1, 7600], ['tap', 2, 8200], ['tap', 3, 8800]]
	}
}, {
	id: 'night_pulse',
	title: 'Night Pulse',
	cover: 'songCover2',
	story: {
		en: "The city lights flicker in rhythm with your heartbeat. Tonight, the music guides your every move.",
		zh: "城市的灯光随着你的心跳闪烁。今夜，音乐引领你的每一步。"
	},
	difficulties: ['Easy', 'Medium', 'Hard'],
	notes: {
		Easy: [['tap', 2, 1000], ['tap', 1, 1800], ['hold', 0, 2600, 1000], ['tap', 3, 4000], ['swipe', 2, 5000, 0, 'left'], ['tap', 1, 6000]],
		Medium: [['tap', 2, 800], ['tap', 1, 1400], ['hold', 0, 2000, 1000], ['tap', 3, 3200], ['swipe', 2, 4000, 0, 'right'], ['tap', 1, 4800], ['tap', 0, 5400], ['hold', 3, 6000, 1200]],
		Hard: [['tap', 2, 600], ['tap', 1, 1000], ['hold', 0, 1400, 1000], ['tap', 3, 2600], ['swipe', 2, 3200, 0, 'up'], ['tap', 1, 3800], ['tap', 0, 4200], ['hold', 3, 4600, 1200], ['tap', 2, 6000], ['swipe', 1, 6600, 0, 'down']]
	}
}, {
	id: 'sunrise_waltz',
	title: 'Sunrise Waltz',
	cover: 'songCover3',
	story: {
		en: "As dawn breaks, melodies dance in the golden light. Every note is a step in your waltz with the sun.",
		zh: "黎明破晓，旋律在金色的光芒中舞动。每一个音符都是你与太阳华尔兹的步伐。"
	},
	difficulties: ['Easy', 'Medium', 'Hard'],
	notes: {
		Easy: [['tap', 1, 1000], ['tap', 2, 1800], ['hold', 3, 2600, 1000], ['tap', 0, 4000], ['swipe', 1, 5000, 0, 'up'], ['tap', 2, 6000]],
		Medium: [['tap', 1, 800], ['tap', 2, 1400], ['hold', 3, 2000, 1000], ['tap', 0, 3200], ['swipe', 1, 4000, 0, 'down'], ['tap', 2, 4800], ['tap', 3, 5400], ['hold', 0, 6000, 1200]],
		Hard: [['tap', 1, 600], ['tap', 2, 1000], ['hold', 3, 1400, 1000], ['tap', 0, 2600], ['swipe', 1, 3200, 0, 'left'], ['tap', 2, 3800], ['tap', 3, 4200], ['hold', 0, 4600, 1200], ['tap', 1, 6000], ['swipe', 2, 6600, 0, 'right']]
	}
}];
// --- GUI ELEMENTS ---
var gui = LK.gui;
var languageButtons = [];
var startButton = null;
var songCards = [];
var storyText = null;
var continueButton = null;
var difficultyButtons = [];
var scoreText = null;
var comboText = null;
var accuracyText = null;
var resultText = null;
var homeButton = null;
// --- GAME ELEMENTS ---
var lanes = [];
var laneDividers = [];
var hitLine = null;
// --- UTILS ---
function clearGUI() {
	// Remove all children from gui overlays
	gui.top.removeChildren();
	gui.topRight.removeChildren();
	gui.topLeft.removeChildren();
	gui.left.removeChildren();
	gui.right.removeChildren();
	gui.bottom.removeChildren();
	gui.bottomLeft.removeChildren();
	gui.bottomRight.removeChildren();
	gui.center.removeChildren();
}
function clearGameObjects() {
	// Remove all notes, lanes, etc.
	for (var i = 0; i < lanes.length; ++i) {
		if (lanes[i].parent) {
			lanes[i].parent.removeChild(lanes[i]);
		}
	}
	for (var i = 0; i < laneDividers.length; ++i) {
		if (laneDividers[i].parent) {
			laneDividers[i].parent.removeChild(laneDividers[i]);
		}
	}
	if (hitLine && hitLine.parent) {
		hitLine.parent.removeChild(hitLine);
	}
	for (var i = 0; i < currentNotes.length; ++i) {
		if (currentNotes[i].parent) {
			currentNotes[i].parent.removeChild(currentNotes[i]);
		}
	}
	currentNotes = [];
}
function setGameState(state) {
	GAME_STATE = state;
	clearGUI();
	clearGameObjects();
	if (state === 'LANGUAGE') {
		showLanguageSelector();
	} else if (state === 'HOME') {
		showHome();
	} else if (state === 'STORY') {
		showStory();
	} else if (state === 'DIFFICULTY') {
		showDifficulty();
	} else if (state === 'PLAY') {
		startGameplay();
	} else if (state === 'RESULT') {
		showResult();
	}
}
// --- LANGUAGE SELECTOR ---
function showLanguageSelector() {
	languageButtons = [];
	// Get current screen size from LK
	var screenWidth = LK.width || 2048;
	var screenHeight = LK.height || 2732;
	// Create opening screen container (with background)
	var openingScreen = new Container();
	// Add background asset, centered
	var bgAsset = LK.getAsset('Openingscreen', {
		anchorX: 0.5,
		anchorY: 0.5,
		x: 0,
		y: 0
	});
	openingScreen.addChild(bgAsset);
	// Add three SelectorUI assets as backgrounds for English, 中文, and play button
	// Calculate button positions and sizes to fit text
	var langBtnYStart = Math.floor(screenHeight * 0.45) - screenHeight / 2;
	var langBtnSpacing = Math.floor(screenHeight * 0.08);
	// English SelectorUI
	var selectorBgEn = LK.getAsset('SelectorUI', {
		anchorX: 0.5,
		anchorY: 0.5,
		x: 0,
		y: langBtnYStart,
		scaleX: 3.2,
		scaleY: 1.3
	});
	openingScreen.addChild(selectorBgEn);
	// 中文 SelectorUI
	var selectorBgZh = LK.getAsset('SelectorUI', {
		anchorX: 0.5,
		anchorY: 0.5,
		x: 0,
		y: langBtnYStart + langBtnSpacing,
		scaleX: 2.2,
		scaleY: 1.3
	});
	openingScreen.addChild(selectorBgZh);
	// Play button SelectorUI
	var playBtnY = Math.floor(screenHeight * 0.70) - screenHeight / 2;
	var selectorBgPlay = LK.getAsset('SelectorUI', {
		anchorX: 0.5,
		anchorY: 0.5,
		x: 0,
		y: playBtnY,
		scaleX: 3.2,
		scaleY: 1.5
	});
	openingScreen.addChild(selectorBgPlay);
	// Center all elements inside the openingScreen container
	// Title
	var titleText = new Text2("Kaleidoscope of Music Rhythm", {
		size: 80,
		fill: "#fff"
	});
	titleText.anchor.set(0.5, 0.5);
	// Place title at 23% of screen height, centered horizontally, and ensure it's not above y=80
	titleText.x = 0;
	titleText.y = Math.max(80 - screenHeight / 2, Math.floor(screenHeight * 0.23) - screenHeight / 2);
	openingScreen.addChild(titleText);
	// Language selector
	var langs = [{
		code: 'en',
		label: 'English'
	}, {
		code: 'zh',
		label: '中文'
	}];
	// Place language buttons at 45% and 53% of screen height, centered horizontally
	var langBtnYStart = Math.floor(screenHeight * 0.45) - screenHeight / 2;
	var langBtnSpacing = Math.floor(screenHeight * 0.08);
	for (var i = 0; i < langs.length; ++i) {
		(function (idx) {
			var btn = new Text2(langs[idx].label, {
				size: 64,
				fill: "#fff"
			});
			btn.anchor.set(0.5, 0.5);
			btn.x = 0; // centered in container
			btn.y = langBtnYStart + idx * langBtnSpacing;
			btn.interactive = true;
			btn.down = function (x, y, obj) {
				selectedLanguage = langs[idx].code;
				storage.language = selectedLanguage;
				// Do not advance to HOME yet, just set language
				clearGUI();
				showLanguageSelector();
			};
			openingScreen.addChild(btn);
			languageButtons.push(btn);
		})(i);
	}
	// Start button
	startButton = new Text2(selectedLanguage === 'zh' ? "开始" : "Start", {
		size: 90,
		fill: "#fff"
	});
	startButton.anchor.set(0.5, 0.5);
	// Place start button at 70% of screen height, centered horizontally
	startButton.x = 0;
	startButton.y = Math.floor(screenHeight * 0.70) - screenHeight / 2;
	startButton.interactive = true;
	startButton.down = function (x, y, obj) {
		setGameState('HOME');
	};
	openingScreen.addChild(startButton);
	// Add the opening screen container to gui.center
	gui.center.addChild(openingScreen);
}
// --- HOME / SONG SELECTION ---
function showHome() {
	clearGUI();
	songCards = [];
	var screenWidth = LK.width || 2048;
	var screenHeight = LK.height || 2732;
	// Create a centered container for the homepage
	var homeScreen = new Container();
	// Title, centered horizontally, upper center, white font
	var title = new Text2(selectedLanguage === 'zh' ? "选择歌曲" : "Select a Song", {
		size: 100,
		fill: "#fff",
		font: "Arial"
	});
	title.anchor.set(0.5, 0.5);
	// Place title at 13% of screen height, centered horizontally, and ensure it's not above y=80
	title.x = 0;
	title.y = Math.max(80 - screenHeight / 2, Math.floor(screenHeight * 0.13) - screenHeight / 2);
	homeScreen.addChild(title);
	// Card layout calculations
	var cardSpacing = 450;
	var cardCount = SONGS.length;
	var cardWidth = 400;
	var totalWidth = (cardCount - 1) * cardSpacing + cardWidth;
	var startX = -totalWidth / 2;
	var cardY = -100;
	// Create song cards and SelectorUI backgrounds
	for (var i = 0; i < SONGS.length; i++) {
		(function (index) {
			var song = SONGS[index];
			// Song card (show cover on homepage)
			var card = new SongCard();
			card.init(song.id, song.cover);
			card.x = startX + index * cardSpacing;
			card.y = cardY;
			card.interactive = true;
			card.down = function (x, y, obj) {
				selectedSong = song;
				setGameState('STORY');
			};
			homeScreen.addChild(card);
			songCards.push(card);
			// SelectorUI background (place behind card, y aligned with card)
			var selectorBg = LK.getAsset('SelectorUI', {
				anchorX: 0.5,
				anchorY: 0.5,
				x: startX + index * cardSpacing,
				y: cardY,
				scaleX: 3.2,
				scaleY: 1.2
			});
			// Add background before card so it is behind
			homeScreen.addChild(selectorBg);
			// Song name text
			var songNameText = new Text2(song.title, {
				size: 64,
				fill: "#fff",
				font: "Arial"
			});
			songNameText.anchor.set(0.5, 0.5);
			songNameText.x = startX + index * cardSpacing;
			songNameText.y = cardY + 300;
			homeScreen.addChild(songNameText);
		})(i);
	}
	// Center the homeScreen container on the screen
	homeScreen.x = screenWidth / 2;
	homeScreen.y = screenHeight / 2;
	// SelectorUI backgrounds are already added before SongCards, so z-order is correct.
	// Add to GUI center layer
	gui.center.addChild(homeScreen);
}
// --- STORY INTRO ---
function showStory() {
	var story = selectedSong.story[selectedLanguage] || selectedSong.story['en'];
	storyText = new Text2(story, {
		size: 70,
		fill: "#fff",
		wordWrap: true,
		wordWrapWidth: 1600
	});
	var screenWidth = LK.width || 2048;
	var screenHeight = LK.height || 2732;
	storyText.anchor.set(0.5, 0.5);
	storyText.x = screenWidth / 2;
	storyText.y = Math.floor(screenHeight * 0.40);
	gui.center.addChild(storyText);
	continueButton = new Text2(selectedLanguage === 'zh' ? "继续" : "Continue", {
		size: 100,
		fill: "#fff"
	});
	continueButton.anchor.set(0.5, 0.5);
	continueButton.x = screenWidth / 2;
	continueButton.y = Math.floor(screenHeight * 0.70);
	continueButton.interactive = true;
	continueButton.down = function (x, y, obj) {
		setGameState('DIFFICULTY');
	};
	gui.center.addChild(continueButton);
}
// --- DIFFICULTY SELECT ---
function showDifficulty() {
	difficultyButtons = [];
	var screenWidth = LK.width || 2048;
	var screenHeight = LK.height || 2732;
	var title = new Text2(selectedLanguage === 'zh' ? "选择难度" : "Select Difficulty", {
		size: 100,
		fill: "#fff"
	});
	title.anchor.set(0.5, 0);
	title.x = screenWidth / 2;
	title.y = Math.max(100, Math.floor(screenHeight * 0.08));
	gui.top.addChild(title);
	var btnYStart = Math.floor(screenHeight * 0.40);
	var btnSpacing = Math.floor(screenHeight * 0.13);
	for (var i = 0; i < selectedSong.difficulties.length; ++i) {
		(function (idx) {
			var label = selectedSong.difficulties[idx];
			var btn = new Text2(label, {
				size: 90,
				fill: "#fff"
			});
			btn.anchor.set(0.5, 0.5);
			btn.x = screenWidth / 2;
			btn.y = btnYStart + idx * btnSpacing;
			btn.interactive = true;
			btn.down = function (x, y, obj) {
				selectedDifficulty = label;
				setGameState('PLAY');
			};
			gui.center.addChild(btn);
			difficultyButtons.push(btn);
		})(i);
	}
}
// --- GAMEPLAY ---
function startGameplay() {
	// Setup lanes
	lanes = [];
	laneDividers = [];
	for (var i = 0; i < LANE_COUNT; ++i) {
		var lane = LK.getAsset('lane', {
			anchorX: 0,
			anchorY: 0
		});
		lane.x = LANE_START_X + i * (LANE_WIDTH + LANE_MARGIN);
		lane.y = 0;
		lanes.push(lane);
		game.addChild(lane);
		if (i > 0) {
			var divider = LK.getAsset('laneDivider', {
				anchorX: 0,
				anchorY: 0
			});
			divider.x = LANE_START_X + i * (LANE_WIDTH + LANE_MARGIN) - LANE_MARGIN / 2 - 10;
			divider.y = 0;
			laneDividers.push(divider);
			game.addChild(divider);
		}
	}
	// Hit line
	hitLine = LK.getAsset('laneDivider', {
		anchorX: 0,
		anchorY: 0
	});
	hitLine.width = 2048;
	hitLine.height = 16;
	hitLine.x = 0;
	hitLine.y = HIT_LINE_Y;
	game.addChild(hitLine);
	// Load notes
	currentSongData = selectedSong.notes[selectedDifficulty];
	currentNotes = [];
	noteIndex = 0;
	score = 0;
	combo = 0;
	maxCombo = 0;
	accuracy = 0;
	totalNotes = currentSongData.length;
	hitNotes = 0;
	missNotes = 0;
	holdActive = null;
	swipeStart = null;
	swipeNote = null;
	isPlaying = true;
	for (var i = 0; i < currentSongData.length; ++i) {
		var n = currentSongData[i];
		var note = new Note();
		note.init(n[0], n[1], n[2], n[3], n[4]);
		// Initial position: y far above screen, will be updated in update loop
		note.x = LANE_START_X + n[1] * (LANE_WIDTH + LANE_MARGIN) + LANE_WIDTH / 2;
		note.y = -200;
		currentNotes.push(note);
		game.addChild(note);
	}
	// Score/Combo/Accuracy GUI
	scoreText = new Text2("Score: 0", {
		size: 80,
		fill: "#fff"
	});
	scoreText.anchor.set(0, 0);
	gui.topRight.addChild(scoreText);
	comboText = new Text2("Combo: 0", {
		size: 80,
		fill: "#fff"
	});
	comboText.anchor.set(0, 0);
	gui.topRight.addChild(comboText);
	accuracyText = new Text2("Accuracy: 100%", {
		size: 80,
		fill: "#fff"
	});
	accuracyText.anchor.set(0, 0);
	gui.topRight.addChild(accuracyText);
	// Start music
	LK.playMusic(selectedSong.id);
	// Start timer
	startTime = Date.now();
}
// --- GAMEPLAY LOGIC ---
function getCurrentTime() {
	return Date.now() - startTime;
}
function getNoteY(noteTime) {
	// Notes fall from y = -200 to HIT_LINE_Y at the time they should be hit
	// We'll use a fixed speed so that notes reach HIT_LINE_Y at noteTime
	var speed = (HIT_LINE_Y + 200) / 2000; // 2 seconds to fall
	var t = getCurrentTime();
	var dt = noteTime - t;
	return HIT_LINE_Y - dt * speed;
}
function getHoldTrailLength(note, t) {
	// For hold notes, trail from note head to end time
	var endTime = note.time + note.duration;
	var y1 = getNoteY(note.time);
	var y2 = getNoteY(endTime);
	return Math.max(0, y2 - y1);
}
function judgeNote(note, lane, y, eventType, swipeDir) {
	if (!note.active || note.hit) {
		return false;
	}
	var noteY = getNoteY(note.time);
	var hitWindow = 120; // ms
	var t = getCurrentTime();
	var dt = Math.abs(note.time - t);
	if (note.type === 'tap') {
		if (lane === note.lane && Math.abs(y - HIT_LINE_Y) < 180 && dt < hitWindow) {
			note.hit = true;
			note.active = false;
			note.flash();
			LK.getSound('tap').play();
			score += 100;
			combo += 1;
			hitNotes += 1;
			maxCombo = Math.max(combo, maxCombo);
			return true;
		}
	} else if (note.type === 'hold') {
		if (eventType === 'down' && lane === note.lane && Math.abs(y - HIT_LINE_Y) < 180 && dt < hitWindow) {
			holdActive = {
				note: note,
				start: t
			};
			note.flash();
			LK.getSound('hold').play();
			return true;
		}
	} else if (note.type === 'swipe') {
		if (eventType === 'swipe' && lane === note.lane && Math.abs(y - HIT_LINE_Y) < 180 && dt < hitWindow && swipeDir === note.swipeDir) {
			note.hit = true;
			note.active = false;
			note.flash();
			LK.getSound('swipe').play();
			score += 150;
			combo += 1;
			hitNotes += 1;
			maxCombo = Math.max(combo, maxCombo);
			return true;
		}
	}
	return false;
}
function endHold() {
	if (holdActive && holdActive.note && !holdActive.note.hit) {
		var t = getCurrentTime();
		var note = holdActive.note;
		var holdEnd = note.time + note.duration;
		if (t >= holdEnd - 150) {
			note.hit = true;
			note.active = false;
			score += 200;
			combo += 1;
			hitNotes += 1;
			maxCombo = Math.max(combo, maxCombo);
		} else {
			combo = 0;
			missNotes += 1;
		}
		holdActive = null;
	}
}
// --- INPUT HANDLING ---
var dragLane = null;
var dragY = null;
var dragNote = null;
var dragStartX = null;
var dragStartY = null;
var dragStartTime = null;
function getLaneFromX(x) {
	for (var i = 0; i < LANE_COUNT; ++i) {
		var lx = LANE_START_X + i * (LANE_WIDTH + LANE_MARGIN);
		if (x >= lx && x < lx + LANE_WIDTH) {
			return i;
		}
	}
	return -1;
}
function handleGameDown(x, y, obj) {
	if (GAME_STATE !== 'PLAY' || !isPlaying) {
		return;
	}
	var lane = getLaneFromX(x);
	if (lane === -1) {
		return;
	}
	dragLane = lane;
	dragY = y;
	dragStartX = x;
	dragStartY = y;
	dragStartTime = Date.now();
	// Check for tap/hold notes
	for (var i = 0; i < currentNotes.length; ++i) {
		var note = currentNotes[i];
		if (!note.active || note.hit) {
			continue;
		}
		if (note.type === 'tap' || note.type === 'hold') {
			if (judgeNote(note, lane, y, 'down')) {
				if (note.type === 'tap') {
					note.hit = true;
					note.active = false;
				}
				if (note.type === 'hold') {
					dragNote = note;
				}
				break;
			}
		}
	}
}
function handleGameUp(x, y, obj) {
	if (GAME_STATE !== 'PLAY' || !isPlaying) {
		return;
	}
	if (holdActive) {
		endHold();
	}
	dragLane = null;
	dragNote = null;
	dragStartX = null;
	dragStartY = null;
	dragStartTime = null;
}
function handleGameMove(x, y, obj) {
	if (GAME_STATE !== 'PLAY' || !isPlaying) {
		return;
	}
	// For hold notes, check if finger is still on lane
	if (holdActive && dragNote) {
		var lane = getLaneFromX(x);
		if (lane !== dragNote.lane || Math.abs(y - HIT_LINE_Y) > 300) {
			// Released too early
			combo = 0;
			missNotes += 1;
			holdActive = null;
			dragNote = null;
		}
	}
}
function handleGameSwipe(x, y, obj) {
	if (GAME_STATE !== 'PLAY' || !isPlaying) {
		return;
	}
	if (dragStartX === null || dragStartY === null) {
		return;
	}
	var dx = x - dragStartX;
	var dy = y - dragStartY;
	var absDx = Math.abs(dx);
	var absDy = Math.abs(dy);
	if (absDx < 80 && absDy < 80) {
		return;
	} // Not enough movement
	var dir = null;
	if (absDx > absDy) {
		dir = dx > 0 ? 'right' : 'left';
	} else {
		dir = dy > 0 ? 'down' : 'up';
	}
	var lane = getLaneFromX(dragStartX);
	for (var i = 0; i < currentNotes.length; ++i) {
		var note = currentNotes[i];
		if (!note.active || note.hit) {
			continue;
		}
		if (note.type === 'swipe') {
			if (judgeNote(note, lane, dragStartY, 'swipe', dir)) {
				break;
			}
		}
	}
	dragStartX = null;
	dragStartY = null;
}
// Attach input handlers
game.down = function (x, y, obj) {
	handleGameDown(x, y, obj);
};
game.up = function (x, y, obj) {
	handleGameUp(x, y, obj);
};
game.move = function (x, y, obj) {
	handleGameMove(x, y, obj);
	// Detect swipe
	if (dragStartX !== null && dragStartY !== null) {
		var dx = x - dragStartX;
		var dy = y - dragStartY;
		if (Math.abs(dx) > 120 || Math.abs(dy) > 120) {
			handleGameSwipe(x, y, obj);
		}
	}
};
// --- GAME UPDATE LOOP ---
game.update = function () {
	if (GAME_STATE !== 'PLAY' || !isPlaying) {
		return;
	}
	var t = getCurrentTime();
	// Update notes
	for (var i = 0; i < currentNotes.length; ++i) {
		var note = currentNotes[i];
		if (!note.active) {
			continue;
		}
		// Update position
		note.x = LANE_START_X + note.lane * (LANE_WIDTH + LANE_MARGIN) + LANE_WIDTH / 2;
		note.y = getNoteY(note.time);
		// For hold notes, update trail
		if (note.type === 'hold' && note.trailAsset) {
			var len = getHoldTrailLength(note, t);
			note.setTrailLength(len);
			note.trailAsset.x = 0;
			note.trailAsset.y = 0;
		}
		// Missed note
		if (!note.hit && t - note.time > 200 && note.type !== 'hold') {
			note.active = false;
			combo = 0;
			missNotes += 1;
		}
		// For hold notes, if not held until end
		if (note.type === 'hold' && !note.hit && t - (note.time + note.duration) > 200) {
			note.active = false;
			combo = 0;
			missNotes += 1;
		}
	}
	// Remove notes that are far below screen
	for (var i = currentNotes.length - 1; i >= 0; --i) {
		var note = currentNotes[i];
		if (note.y > 3000 || !note.active && note.y > HIT_LINE_Y + 400) {
			if (note.parent) {
				note.parent.removeChild(note);
			}
			currentNotes.splice(i, 1);
		}
	}
	// Update GUI
	scoreText.setText("Score: " + score);
	comboText.setText("Combo: " + combo);
	var acc = totalNotes > 0 ? Math.floor(100 * hitNotes / totalNotes) : 100;
	accuracyText.setText("Accuracy: " + acc + "%");
	// End of song
	if (t > getSongEndTime() + 1000 && isPlaying) {
		isPlaying = false;
		LK.stopMusic();
		resultTimeout = LK.setTimeout(function () {
			setGameState('RESULT');
		}, 1200);
	}
};
function getSongEndTime() {
	var last = currentSongData[currentSongData.length - 1];
	if (!last) {
		return 0;
	}
	if (last[0] === 'hold') {
		return last[2] + last[3];
	}
	return last[2] + 1000;
}
// --- RESULT SCREEN ---
function showResult() {
	clearGameObjects();
	var acc = totalNotes > 0 ? Math.floor(100 * hitNotes / totalNotes) : 100;
	var resultStr = (selectedLanguage === 'zh' ? "结果" : "Result") + "\n";
	resultStr += (selectedLanguage === 'zh' ? "分数: " : "Score: ") + score + "\n";
	resultStr += (selectedLanguage === 'zh' ? "最大连击: " : "Max Combo: ") + maxCombo + "\n";
	resultStr += (selectedLanguage === 'zh' ? "准确率: " : "Accuracy: ") + acc + "%\n";
	resultStr += (selectedLanguage === 'zh' ? "命中: " : "Hit: ") + hitNotes + "/" + totalNotes + "\n";
	resultStr += (selectedLanguage === 'zh' ? "未命中: " : "Miss: ") + missNotes;
	resultText = new Text2(resultStr, {
		size: 90,
		fill: "#fff",
		align: "center"
	});
	var screenWidth = LK.width || 2048;
	var screenHeight = LK.height || 2732;
	resultText.anchor.set(0.5, 0.5);
	resultText.x = screenWidth / 2;
	resultText.y = Math.floor(screenHeight * 0.36);
	gui.center.addChild(resultText);
	homeButton = new Text2(selectedLanguage === 'zh' ? "返回首页" : "Home", {
		size: 100,
		fill: "#fff"
	});
	homeButton.anchor.set(0.5, 0.5);
	homeButton.x = screenWidth / 2;
	homeButton.y = Math.floor(screenHeight * 0.66);
	homeButton.interactive = true;
	homeButton.down = function (x, y, obj) {
		setGameState('HOME');
	};
	gui.center.addChild(homeButton);
}
// --- START GAME ---
// Start at language selector (opening screen)
setGameState('LANGUAGE');

===================================================================
--- original.js
+++ change.js
@@ -421,10 +421,10 @@
 				y: cardY,
 				scaleX: 3.2,
 				scaleY: 1.2
 			});
-			// Insert background behind card
-			homeScreen.setChildIndex(selectorBg, homeScreen.children.indexOf(card));
+			// Add background before card so it is behind
+			homeScreen.addChild(selectorBg);
 			// Song name text
 			var songNameText = new Text2(song.title, {
 				size: 64,
 				fill: "#fff",
@@ -438,18 +438,9 @@
 	}
 	// Center the homeScreen container on the screen
 	homeScreen.x = screenWidth / 2;
 	homeScreen.y = screenHeight / 2;
-	// Ensure SelectorUI backgrounds are always behind SongCards
-	for (var i = 0; i < songCards.length; i++) {
-		var card = songCards[i];
-		for (var j = 0; j < homeScreen.children.length; j++) {
-			var child = homeScreen.children[j];
-			if (child !== card && child.assetId === 'SelectorUI' && child.x === card.x && child.y === card.y) {
-				homeScreen.setChildIndex(child, homeScreen.children.indexOf(card));
-			}
-		}
-	}
+	// SelectorUI backgrounds are already added before SongCards, so z-order is correct.
 	// Add to GUI center layer
 	gui.center.addChild(homeScreen);
 }
 // --- STORY INTRO ---