/**** 
* Plugins
****/ 
var tween = LK.import("@upit/tween.v1");

/**** 
* Classes
****/ 
var Bullet = Container.expand(function () {
	var self = Container.call(this);
	var bulletGraphics = self.attachAsset('bullet', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 8;
	self.damage = 25;
	self.target = null;
	self.hasHit = false;
	self.update = function () {
		if (!self.target || self.hasHit) return;
		var dx = self.target.x - self.x;
		var dy = self.target.y - self.y;
		var distance = Math.sqrt(dx * dx + dy * dy);
		if (distance < 20) {
			self.target.takeDamage(self.damage);
			self.hasHit = true;
			LK.getSound('enemyHit').play();
			return;
		}
		var moveX = dx / distance * self.speed;
		var moveY = dy / distance * self.speed;
		self.x += moveX;
		self.y += moveY;
	};
	return self;
});
var Enemy = Container.expand(function () {
	var self = Container.call(this);
	var enemyGraphics = self.attachAsset('enemy', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.maxHealth = 100;
	self.health = self.maxHealth;
	self.speed = 2;
	self.reward = 10;
	self.pathIndex = 0;
	self.isDead = false;
	self.reachedBase = false;
	// Add health bar
	var healthBarBg = LK.getAsset('pathTile', {
		anchorX: 0.5,
		anchorY: 0.5,
		scaleX: 0.6,
		scaleY: 0.1
	});
	healthBarBg.y = -40;
	healthBarBg.tint = 0x333333;
	self.addChild(healthBarBg);
	var healthBar = LK.getAsset('grassTile', {
		anchorX: 0.5,
		anchorY: 0.5,
		scaleX: 0.6,
		scaleY: 0.1
	});
	healthBar.y = -40;
	healthBar.tint = 0x00FF00;
	self.addChild(healthBar);
	self.updateHealthBar = function () {
		var healthPercent = self.health / self.maxHealth;
		healthBar.scaleX = 0.6 * healthPercent;
		if (healthPercent > 0.6) {
			healthBar.tint = 0x00FF00; // Green
		} else if (healthPercent > 0.3) {
			healthBar.tint = 0xFFFF00; // Yellow
		} else {
			healthBar.tint = 0xFF0000; // Red
		}
	};
	self.takeDamage = function (damage) {
		self.health -= damage;
		self.updateHealthBar();
		if (self.health <= 0 && !self.isDead) {
			self.isDead = true;
			LK.getSound('enemyDeath').play();
			currency += self.reward;
			updateUI();
			// Death animation
			tween.to(enemyGraphics, {
				alpha: 0,
				scaleX: 0.1,
				scaleY: 0.1
			}, 500);
		}
	};
	self.update = function () {
		if (self.isDead || self.reachedBase) return;
		if (self.pathIndex < enemyPath.length) {
			var target = enemyPath[self.pathIndex];
			var dx = target.x - self.x;
			var dy = target.y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			if (distance < 20) {
				self.pathIndex++;
				if (self.pathIndex >= enemyPath.length) {
					self.reachedBase = true;
					lives--;
					updateUI();
					return;
				}
			}
			var moveX = dx / distance * self.speed;
			var moveY = dy / distance * self.speed;
			self.x += moveX;
			self.y += moveY;
		}
	};
	return self;
});
var Tower = Container.expand(function () {
	var self = Container.call(this);
	var towerGraphics = self.attachAsset('tower', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.range = 150;
	self.damage = 25;
	self.fireRate = 60;
	self.lastFire = 0;
	self.cost = 50;
	self.level = 1;
	self.maxLevel = 3;
	self.showingRange = false;
	self.upgradeCost = 75;
	var rangeIndicator = self.attachAsset('towerRange', {
		anchorX: 0.5,
		anchorY: 0.5,
		alpha: 0.3
	});
	rangeIndicator.width = self.range * 2;
	rangeIndicator.height = self.range * 2;
	rangeIndicator.visible = false;
	self.showRange = function () {
		rangeIndicator.visible = true;
		self.showingRange = true;
	};
	self.hideRange = function () {
		rangeIndicator.visible = false;
		self.showingRange = false;
	};
	self.findTarget = function () {
		var closestEnemy = null;
		var closestDistance = Infinity;
		for (var i = 0; i < enemies.length; i++) {
			var enemy = enemies[i];
			if (enemy.isDead || enemy.reachedBase) continue;
			var dx = enemy.x - self.x;
			var dy = enemy.y - self.y;
			var distance = Math.sqrt(dx * dx + dy * dy);
			if (distance <= self.range && distance < closestDistance) {
				closestDistance = distance;
				closestEnemy = enemy;
			}
		}
		return closestEnemy;
	};
	self.fire = function (target) {
		if (LK.ticks - self.lastFire < self.fireRate) return;
		var bullet = new Bullet();
		bullet.x = self.x;
		bullet.y = self.y;
		bullet.target = target;
		bullet.damage = self.damage;
		bullets.push(bullet);
		game.addChild(bullet);
		self.lastFire = LK.ticks;
		LK.getSound('shoot').play();
	};
	self.upgrade = function () {
		if (self.level >= self.maxLevel || currency < self.upgradeCost) return false;
		currency -= self.upgradeCost;
		self.level++;
		self.damage += 15;
		self.range += 25;
		self.fireRate = Math.max(30, self.fireRate - 10);
		self.upgradeCost = Math.floor(self.upgradeCost * 1.5);
		// Update range indicator
		rangeIndicator.width = self.range * 2;
		rangeIndicator.height = self.range * 2;
		// Visual upgrade indicator
		towerGraphics.tint = self.level === 2 ? 0x3A7BD5 : 0x2E5BBA;
		updateUI();
		return true;
	};
	self.down = function (x, y, obj) {
		if (selectedTower === self) {
			// Try to upgrade if tower is selected
			if (self.level < self.maxLevel && currency >= self.upgradeCost) {
				self.upgrade();
			}
			selectedTower = null;
			hideAllRanges();
		} else {
			// Select this tower
			selectedTower = self;
			hideAllRanges();
			self.showRange();
		}
	};
	self.update = function () {
		var target = self.findTarget();
		if (target) {
			self.fire(target);
		}
	};
	return self;
});

/**** 
* Initialize Game
****/ 
var game = new LK.Game({
	backgroundColor: 0x87CEEB
});

/**** 
* Game Code
****/ 
var gridSize = 100;
var mapWidth = 20;
var mapHeight = 25;
var currency = 100;
var lives = 20;
var wave = 1;
var enemiesInWave = 5;
var enemiesSpawned = 0;
var waveActive = false;
var gameOver = false;
var towers = [];
var enemies = [];
var bullets = [];
var grid = [];
var enemyPath = [];
var selectedTower = null;
var placingTower = false;
// Create UI elements
var currencyTxt = new Text2('Gold: 100', {
	size: 60,
	fill: 0xFFD700
});
currencyTxt.anchor.set(0, 0);
currencyTxt.x = 120;
currencyTxt.y = 20;
LK.gui.topLeft.addChild(currencyTxt);
var livesTxt = new Text2('Lives: 20', {
	size: 60,
	fill: 0xFF0000
});
livesTxt.anchor.set(0.5, 0);
LK.gui.top.addChild(livesTxt);
var waveTxt = new Text2('Wave: 1', {
	size: 60,
	fill: 0xFFFFFF
});
waveTxt.anchor.set(1, 0);
LK.gui.topRight.addChild(waveTxt);
var startWaveBtn = new Text2('Start Wave', {
	size: 80,
	fill: 0x00FF00
});
startWaveBtn.anchor.set(0.5, 1);
startWaveBtn.y = -20;
LK.gui.bottom.addChild(startWaveBtn);
var buyTowerBtn = new Text2('Buy Tower (50g)', {
	size: 70,
	fill: 0x4A90E2
});
buyTowerBtn.anchor.set(0, 1);
buyTowerBtn.x = 20;
buyTowerBtn.y = -20;
LK.gui.bottomLeft.addChild(buyTowerBtn);
var upgradeTowerBtn = new Text2('Upgrade Tower', {
	size: 70,
	fill: 0xFF6B35
});
upgradeTowerBtn.anchor.set(0, 1);
upgradeTowerBtn.x = 20;
upgradeTowerBtn.y = -100;
upgradeTowerBtn.visible = false;
LK.gui.bottomLeft.addChild(upgradeTowerBtn);
function updateUI() {
	currencyTxt.setText('Gold: ' + currency);
	livesTxt.setText('Lives: ' + lives);
	waveTxt.setText('Wave: ' + wave);
	if (currency >= 50) {
		buyTowerBtn.tint = 0x4A90E2;
	} else {
		buyTowerBtn.tint = 0x666666;
	}
	// Update upgrade button visibility and state
	if (selectedTower && selectedTower.level < selectedTower.maxLevel) {
		upgradeTowerBtn.visible = true;
		upgradeTowerBtn.setText('Upgrade Lv' + selectedTower.level + ' (' + selectedTower.upgradeCost + 'g)');
		if (currency >= selectedTower.upgradeCost) {
			upgradeTowerBtn.tint = 0xFF6B35;
		} else {
			upgradeTowerBtn.tint = 0x666666;
		}
	} else {
		upgradeTowerBtn.visible = false;
	}
}
function hideAllRanges() {
	for (var i = 0; i < towers.length; i++) {
		towers[i].hideRange();
	}
}
function initializeGrid() {
	for (var x = 0; x < mapWidth; x++) {
		grid[x] = [];
		for (var y = 0; y < mapHeight; y++) {
			grid[x][y] = {
				x: x * gridSize + gridSize / 2,
				y: y * gridSize + gridSize / 2,
				occupied: false,
				isPath: false
			};
		}
	}
}
function createPath() {
	enemyPath = [];
	var pathCoords = [{
		x: 0,
		y: 12
	}, {
		x: 1,
		y: 12
	}, {
		x: 2,
		y: 12
	}, {
		x: 3,
		y: 12
	}, {
		x: 4,
		y: 12
	}, {
		x: 5,
		y: 12
	}, {
		x: 6,
		y: 12
	}, {
		x: 7,
		y: 12
	}, {
		x: 8,
		y: 12
	}, {
		x: 8,
		y: 11
	}, {
		x: 8,
		y: 10
	}, {
		x: 8,
		y: 9
	}, {
		x: 8,
		y: 8
	}, {
		x: 9,
		y: 8
	}, {
		x: 10,
		y: 8
	}, {
		x: 11,
		y: 8
	}, {
		x: 12,
		y: 8
	}, {
		x: 12,
		y: 9
	}, {
		x: 12,
		y: 10
	}, {
		x: 12,
		y: 11
	}, {
		x: 12,
		y: 12
	}, {
		x: 13,
		y: 12
	}, {
		x: 14,
		y: 12
	}, {
		x: 15,
		y: 12
	}, {
		x: 16,
		y: 12
	}, {
		x: 17,
		y: 12
	}, {
		x: 18,
		y: 12
	}, {
		x: 19,
		y: 12
	}];
	for (var i = 0; i < pathCoords.length; i++) {
		var coord = pathCoords[i];
		if (coord.x < mapWidth && coord.y < mapHeight) {
			grid[coord.x][coord.y].isPath = true;
			enemyPath.push({
				x: coord.x * gridSize + gridSize / 2,
				y: coord.y * gridSize + gridSize / 2
			});
		}
	}
}
function drawMap() {
	for (var x = 0; x < mapWidth; x++) {
		for (var y = 0; y < mapHeight; y++) {
			var tile;
			if (grid[x][y].isPath) {
				tile = LK.getAsset('pathTile', {
					x: x * gridSize,
					y: y * gridSize
				});
			} else {
				tile = LK.getAsset('grassTile', {
					x: x * gridSize,
					y: y * gridSize
				});
			}
			game.addChild(tile);
		}
	}
}
function drawBase() {
	var base = LK.getAsset('base', {
		anchorX: 0.5,
		anchorY: 0.5,
		x: (mapWidth - 1) * gridSize + gridSize / 2,
		y: 12 * gridSize + gridSize / 2
	});
	game.addChild(base);
}
function spawnEnemy() {
	if (enemiesSpawned >= enemiesInWave) return;
	var enemy = new Enemy();
	enemy.x = gridSize / 2;
	enemy.y = 12 * gridSize + gridSize / 2;
	enemy.health = 100 + (wave - 1) * 20;
	enemy.maxHealth = enemy.health;
	enemy.speed = 1.5 + (wave - 1) * 0.2;
	enemy.reward = 10 + (wave - 1) * 2;
	enemies.push(enemy);
	game.addChild(enemy);
	enemiesSpawned++;
}
function getGridPosition(x, y) {
	var gridX = Math.floor(x / gridSize);
	var gridY = Math.floor(y / gridSize);
	if (gridX >= 0 && gridX < mapWidth && gridY >= 0 && gridY < mapHeight) {
		return {
			x: gridX,
			y: gridY
		};
	}
	return null;
}
function canPlaceTower(gridX, gridY) {
	return !grid[gridX][gridY].occupied && !grid[gridX][gridY].isPath;
}
function placeTower(gridX, gridY) {
	if (!canPlaceTower(gridX, gridY) || currency < 50) return false;
	var tower = new Tower();
	tower.x = gridX * gridSize + gridSize / 2;
	tower.y = gridY * gridSize + gridSize / 2;
	towers.push(tower);
	game.addChild(tower);
	grid[gridX][gridY].occupied = true;
	currency -= tower.cost;
	placingTower = false;
	updateUI();
	return true;
}
function startWave() {
	if (waveActive) return;
	waveActive = true;
	enemiesSpawned = 0;
	enemiesInWave = 5 + wave * 2;
	startWaveBtn.setText('Wave Active');
	startWaveBtn.tint = 0x666666;
}
function checkWaveComplete() {
	if (!waveActive) return;
	var allEnemiesGone = true;
	for (var i = 0; i < enemies.length; i++) {
		if (!enemies[i].isDead && !enemies[i].reachedBase) {
			allEnemiesGone = false;
			break;
		}
	}
	if (enemiesSpawned >= enemiesInWave && allEnemiesGone) {
		waveActive = false;
		wave++;
		currency += 25;
		startWaveBtn.setText('Start Wave');
		startWaveBtn.tint = 0x00FF00;
		updateUI();
		// Clean up dead enemies
		for (var i = enemies.length - 1; i >= 0; i--) {
			if (enemies[i].isDead || enemies[i].reachedBase) {
				enemies[i].destroy();
				enemies.splice(i, 1);
			}
		}
	}
}
// Initialize game
initializeGrid();
createPath();
drawMap();
drawBase();
updateUI();
// Event handlers
startWaveBtn.down = function () {
	startWave();
};
buyTowerBtn.down = function () {
	if (currency >= 50) {
		placingTower = true;
		selectedTower = null;
		hideAllRanges();
		updateUI();
	}
};
upgradeTowerBtn.down = function () {
	if (selectedTower && selectedTower.upgrade()) {
		updateUI();
	}
};
game.down = function (x, y, obj) {
	if (placingTower) {
		var gridPos = getGridPosition(x, y);
		if (gridPos) {
			placeTower(gridPos.x, gridPos.y);
		}
	} else {
		// Clear tower selection if clicking on empty space
		var gridPos = getGridPosition(x, y);
		if (gridPos && !grid[gridPos.x][gridPos.y].occupied) {
			selectedTower = null;
			hideAllRanges();
			updateUI();
		}
	}
};
// Main game loop
game.update = function () {
	if (lives <= 0 && !gameOver) {
		gameOver = true;
		LK.showGameOver();
		return;
	}
	if (wave > 20) {
		LK.showYouWin();
		return;
	}
	// Spawn enemies during wave with decreasing interval
	var spawnInterval = Math.max(45, 90 - wave * 2);
	if (waveActive && LK.ticks % spawnInterval === 0) {
		spawnEnemy();
	}
	// Clean up bullets that hit targets
	for (var i = bullets.length - 1; i >= 0; i--) {
		var bullet = bullets[i];
		if (bullet.hasHit || !bullet.target || bullet.target.isDead) {
			bullet.destroy();
			bullets.splice(i, 1);
		}
	}
	checkWaveComplete();
};

===================================================================
--- original.js
+++ change.js
@@ -46,15 +46,52 @@
 	self.reward = 10;
 	self.pathIndex = 0;
 	self.isDead = false;
 	self.reachedBase = false;
+	// Add health bar
+	var healthBarBg = LK.getAsset('pathTile', {
+		anchorX: 0.5,
+		anchorY: 0.5,
+		scaleX: 0.6,
+		scaleY: 0.1
+	});
+	healthBarBg.y = -40;
+	healthBarBg.tint = 0x333333;
+	self.addChild(healthBarBg);
+	var healthBar = LK.getAsset('grassTile', {
+		anchorX: 0.5,
+		anchorY: 0.5,
+		scaleX: 0.6,
+		scaleY: 0.1
+	});
+	healthBar.y = -40;
+	healthBar.tint = 0x00FF00;
+	self.addChild(healthBar);
+	self.updateHealthBar = function () {
+		var healthPercent = self.health / self.maxHealth;
+		healthBar.scaleX = 0.6 * healthPercent;
+		if (healthPercent > 0.6) {
+			healthBar.tint = 0x00FF00; // Green
+		} else if (healthPercent > 0.3) {
+			healthBar.tint = 0xFFFF00; // Yellow
+		} else {
+			healthBar.tint = 0xFF0000; // Red
+		}
+	};
 	self.takeDamage = function (damage) {
 		self.health -= damage;
+		self.updateHealthBar();
 		if (self.health <= 0 && !self.isDead) {
 			self.isDead = true;
 			LK.getSound('enemyDeath').play();
 			currency += self.reward;
 			updateUI();
+			// Death animation
+			tween.to(enemyGraphics, {
+				alpha: 0,
+				scaleX: 0.1,
+				scaleY: 0.1
+			}, 500);
 		}
 	};
 	self.update = function () {
 		if (self.isDead || self.reachedBase) return;
@@ -91,9 +128,11 @@
 	self.fireRate = 60;
 	self.lastFire = 0;
 	self.cost = 50;
 	self.level = 1;
+	self.maxLevel = 3;
 	self.showingRange = false;
+	self.upgradeCost = 75;
 	var rangeIndicator = self.attachAsset('towerRange', {
 		anchorX: 0.5,
 		anchorY: 0.5,
 		alpha: 0.3
@@ -136,12 +175,36 @@
 		game.addChild(bullet);
 		self.lastFire = LK.ticks;
 		LK.getSound('shoot').play();
 	};
+	self.upgrade = function () {
+		if (self.level >= self.maxLevel || currency < self.upgradeCost) return false;
+		currency -= self.upgradeCost;
+		self.level++;
+		self.damage += 15;
+		self.range += 25;
+		self.fireRate = Math.max(30, self.fireRate - 10);
+		self.upgradeCost = Math.floor(self.upgradeCost * 1.5);
+		// Update range indicator
+		rangeIndicator.width = self.range * 2;
+		rangeIndicator.height = self.range * 2;
+		// Visual upgrade indicator
+		towerGraphics.tint = self.level === 2 ? 0x3A7BD5 : 0x2E5BBA;
+		updateUI();
+		return true;
+	};
 	self.down = function (x, y, obj) {
-		if (self.showingRange) {
-			self.hideRange();
+		if (selectedTower === self) {
+			// Try to upgrade if tower is selected
+			if (self.level < self.maxLevel && currency >= self.upgradeCost) {
+				self.upgrade();
+			}
+			selectedTower = null;
+			hideAllRanges();
 		} else {
+			// Select this tower
+			selectedTower = self;
+			hideAllRanges();
 			self.showRange();
 		}
 	};
 	self.update = function () {
@@ -215,8 +278,17 @@
 buyTowerBtn.anchor.set(0, 1);
 buyTowerBtn.x = 20;
 buyTowerBtn.y = -20;
 LK.gui.bottomLeft.addChild(buyTowerBtn);
+var upgradeTowerBtn = new Text2('Upgrade Tower', {
+	size: 70,
+	fill: 0xFF6B35
+});
+upgradeTowerBtn.anchor.set(0, 1);
+upgradeTowerBtn.x = 20;
+upgradeTowerBtn.y = -100;
+upgradeTowerBtn.visible = false;
+LK.gui.bottomLeft.addChild(upgradeTowerBtn);
 function updateUI() {
 	currencyTxt.setText('Gold: ' + currency);
 	livesTxt.setText('Lives: ' + lives);
 	waveTxt.setText('Wave: ' + wave);
@@ -224,9 +296,26 @@
 		buyTowerBtn.tint = 0x4A90E2;
 	} else {
 		buyTowerBtn.tint = 0x666666;
 	}
+	// Update upgrade button visibility and state
+	if (selectedTower && selectedTower.level < selectedTower.maxLevel) {
+		upgradeTowerBtn.visible = true;
+		upgradeTowerBtn.setText('Upgrade Lv' + selectedTower.level + ' (' + selectedTower.upgradeCost + 'g)');
+		if (currency >= selectedTower.upgradeCost) {
+			upgradeTowerBtn.tint = 0xFF6B35;
+		} else {
+			upgradeTowerBtn.tint = 0x666666;
+		}
+	} else {
+		upgradeTowerBtn.visible = false;
+	}
 }
+function hideAllRanges() {
+	for (var i = 0; i < towers.length; i++) {
+		towers[i].hideRange();
+	}
+}
 function initializeGrid() {
 	for (var x = 0; x < mapWidth; x++) {
 		grid[x] = [];
 		for (var y = 0; y < mapHeight; y++) {
@@ -240,18 +329,102 @@
 	}
 }
 function createPath() {
 	enemyPath = [];
-	var startX = 0;
-	var startY = Math.floor(mapHeight / 2);
-	var endX = mapWidth - 1;
-	var endY = Math.floor(mapHeight / 2);
-	for (var x = startX; x <= endX; x++) {
-		grid[x][startY].isPath = true;
-		enemyPath.push({
-			x: x * gridSize + gridSize / 2,
-			y: startY * gridSize + gridSize / 2
-		});
+	var pathCoords = [{
+		x: 0,
+		y: 12
+	}, {
+		x: 1,
+		y: 12
+	}, {
+		x: 2,
+		y: 12
+	}, {
+		x: 3,
+		y: 12
+	}, {
+		x: 4,
+		y: 12
+	}, {
+		x: 5,
+		y: 12
+	}, {
+		x: 6,
+		y: 12
+	}, {
+		x: 7,
+		y: 12
+	}, {
+		x: 8,
+		y: 12
+	}, {
+		x: 8,
+		y: 11
+	}, {
+		x: 8,
+		y: 10
+	}, {
+		x: 8,
+		y: 9
+	}, {
+		x: 8,
+		y: 8
+	}, {
+		x: 9,
+		y: 8
+	}, {
+		x: 10,
+		y: 8
+	}, {
+		x: 11,
+		y: 8
+	}, {
+		x: 12,
+		y: 8
+	}, {
+		x: 12,
+		y: 9
+	}, {
+		x: 12,
+		y: 10
+	}, {
+		x: 12,
+		y: 11
+	}, {
+		x: 12,
+		y: 12
+	}, {
+		x: 13,
+		y: 12
+	}, {
+		x: 14,
+		y: 12
+	}, {
+		x: 15,
+		y: 12
+	}, {
+		x: 16,
+		y: 12
+	}, {
+		x: 17,
+		y: 12
+	}, {
+		x: 18,
+		y: 12
+	}, {
+		x: 19,
+		y: 12
+	}];
+	for (var i = 0; i < pathCoords.length; i++) {
+		var coord = pathCoords[i];
+		if (coord.x < mapWidth && coord.y < mapHeight) {
+			grid[coord.x][coord.y].isPath = true;
+			enemyPath.push({
+				x: coord.x * gridSize + gridSize / 2,
+				y: coord.y * gridSize + gridSize / 2
+			});
+		}
 	}
 }
 function drawMap() {
 	for (var x = 0; x < mapWidth; x++) {
@@ -276,17 +449,17 @@
 	var base = LK.getAsset('base', {
 		anchorX: 0.5,
 		anchorY: 0.5,
 		x: (mapWidth - 1) * gridSize + gridSize / 2,
-		y: Math.floor(mapHeight / 2) * gridSize + gridSize / 2
+		y: 12 * gridSize + gridSize / 2
 	});
 	game.addChild(base);
 }
 function spawnEnemy() {
 	if (enemiesSpawned >= enemiesInWave) return;
 	var enemy = new Enemy();
 	enemy.x = gridSize / 2;
-	enemy.y = Math.floor(mapHeight / 2) * gridSize + gridSize / 2;
+	enemy.y = 12 * gridSize + gridSize / 2;
 	enemy.health = 100 + (wave - 1) * 20;
 	enemy.maxHealth = enemy.health;
 	enemy.speed = 1.5 + (wave - 1) * 0.2;
 	enemy.reward = 10 + (wave - 1) * 2;
@@ -366,19 +539,32 @@
 };
 buyTowerBtn.down = function () {
 	if (currency >= 50) {
 		placingTower = true;
-		for (var i = 0; i < towers.length; i++) {
-			towers[i].hideRange();
-		}
+		selectedTower = null;
+		hideAllRanges();
+		updateUI();
 	}
 };
+upgradeTowerBtn.down = function () {
+	if (selectedTower && selectedTower.upgrade()) {
+		updateUI();
+	}
+};
 game.down = function (x, y, obj) {
 	if (placingTower) {
 		var gridPos = getGridPosition(x, y);
 		if (gridPos) {
 			placeTower(gridPos.x, gridPos.y);
 		}
+	} else {
+		// Clear tower selection if clicking on empty space
+		var gridPos = getGridPosition(x, y);
+		if (gridPos && !grid[gridPos.x][gridPos.y].occupied) {
+			selectedTower = null;
+			hideAllRanges();
+			updateUI();
+		}
 	}
 };
 // Main game loop
 game.update = function () {
@@ -390,10 +576,11 @@
 	if (wave > 20) {
 		LK.showYouWin();
 		return;
 	}
-	// Spawn enemies during wave
-	if (waveActive && LK.ticks % 90 === 0) {
+	// Spawn enemies during wave with decreasing interval
+	var spawnInterval = Math.max(45, 90 - wave * 2);
+	if (waveActive && LK.ticks % spawnInterval === 0) {
 		spawnEnemy();
 	}
 	// Clean up bullets that hit targets
 	for (var i = bullets.length - 1; i >= 0; i--) {